Post by MADMIKE on Jun 4, 2007 15:19:12 GMT -5
zebra plecos
Length = Length of the fish;
Width = Body width + 2/3 of the length of the pectoral fin;
Height = Height of the body + 2/3 of the height of the dorsal fin.
If you want to spare yourself the measurement of your fish, you can use the measurements of 3.5 x 1.0 x 0.6 inches (L x W x H) for a cave to accommodate full-grown fish. For younger fish you should select accordingly smaller caves. Most other loricariids also accept these caves very well.
Eventually, the location of the cave also is of importance. Rickhoff made the observation that his zebras mostly received a strong current from the filter. Perhaps the caves were selected so that the eggs and young get the optimum amount of fresh water and oxygen. This is only a supposition, but one that tallies completely with my observations.
A male in one of the specially constructed breeding caves.
Spawning
As a rule, the caves are accepted by the fish soon after they are placed in the tank. In a broad sense, the spawning of Hypancistrus resembles that of the bristlenose plecos of the genus Ancistrus, but there are differences. Whereas spawning readiness in Ancistrus males is announced by wagging with the paired fins in front of the cave, Hypancistrus males exhibit little activity beforehand. You will simple notice all of a sudden that the fish have paired off.
According to Karin & Gerd Arndt, the egglaying behavior resembles very strongly that of Ancistrus species. The zebras often lay on top of each other in the cave. Finally, the male lays sideways with his caudal fin and half of his body on the head of the female. She produces her eggs in several batches. The male blocks the cave entrance with his head. After each group of eggs is laid, the female makes fidgety forward and backward movements to signal to the male that the eggs can now be fertilized. Since the female often will not leave the cave after spawning is over, she occasionally must be pushed out by the male.
The eggs are deposited in the slate cave mostly in the outermost corner, on the bottom. Whether the males mouth the eggs, as in Ancistrus, has not yet been observed. The fanning movements with the pelvic fins are sporadic. When “danger” threatens (for example, when a flashlight is shined into the cave) the male covers the egg mass almost completely, so that at most only one to two eggs can be seen.
The Arndts’s zebra plecos spawned on 10 June 1994 for the first time. Unfortunately, they had little luck, since on 13 June the empty eggshells lay in front of the cave. Probably this spawn was not fertilized. There was no basis for worry, however, since in other loricariids there are many cases in which the first spawn in not fertilized.
The second spawn went better. The eggs were laid on the evening of 13 June. In spite of frequent inspections the next day, the exact number could not be determined. On 18 June, six fry with enormous yolk sacks were sighted outside of the cave and were siphoned out. The fry were transferred to a net-covered breeder box hung inside the tank in the filter current. Unfortunately, three of the young died after a short time. On 23 June the male once more was seen sitting on a spawn, and on 24 June a second male in another hole did the same. Since then the Arndts have had their zebras producing pretty regularly.
As I mentioned earlier, the spawning of my H. zebra happened very unexpectedly. I kept three fish for than two years, but in the end they reached a size of about 3.6 inches and all were obviously males. Therefore, I expanded my H. zebra stock in the late summer of last year with about five additional fish, all of which were smaller. After their quarantine I still did not place them with the full-grown males, since to me they simply appeared much too small to be able to spawn with them. So, I placed them in a 75-gallon tank for grow-out, along with five large Pseudohemiodon laticeps and some Ancistrus sp. Apart from some plants in clay pots and some slate, there were only two of the specially made spawning caves. The zebra plecos hid mostly under the slate or behind the filter. After several months, however, the largest specimen, a male, had reached a size of 2.6 inches and showed interest in the cave. It even selected the larger of the two caves, manageing to chase away the larger Ancistrus. After two days, a somewhat smaller zebra was staying near the male. Obviously this was a female. Soon, she entered the cave with the male. I could not quite believe that the fish were spawning at this small size, and so the next day I turned the cave somewhat in order to be able to light it for photography. The frightened male performed some jerky movements, and to my total shock, 12 eggs were dislodged from the cave.
Since I had had previous experience with artificial rearing of other loricariids, I had no great concern about the eggs. I transferred them carefully into a small Plexiglas tank that was filled with aged fresh water. In order to maintain the proper temperature, it was simply hung in the adults’ tank. An airstone provided the necessary oxygen supply. For prevention of fungus I added acriflavine. After a day, it was apparent that two eggs were bad. I prodded these eggs with a pipette and sucked the contents out completely so that only the shells remained. This measure is necessary because the eggs stick so strongly together that the bad eggs cannot be separated without risking damage to the good ones. Afterward I did a complete water change in the brooder box. After four days it could be seen that another egg showed no development. This egg was also siphoned out. At 86oF, nine fry hatched on the seventh day. In a second spawn, about four weeks later, my artificial rearing was more successful; I managed to get 11 fry out of 12 eggs.
Development of Eggs and Young
In nearly all of the ancistrine loricariids that have been spawned to date, the eggs are yellow in color. When you see the eggs of the zebra pleco for the first time, on the basis of their milky white coloration you would think that they were infertile. The size of the eggs also is a curiosity. The egg diameter, according to the age and feeding condition of the female, can vary between 4 and 5 mm. Interestingly, larger loricariids, such as the Ancistrus species or Lasiancistrus scolymus (see Elsholz & Elsholz, 1992), usually have smaller eggs. Accordingly, however, the number of eggs is small. In past broods the number varied between 7 and 12 eggs. I expect, however, that fully grown females that are well fed might be able to lay up to 20 eggs.
Seven days. Eight days. Nine days.
Immediately after they are laid, hardly any structures are recognizably in the interior of these eggs. After one day, however, the body of the embryo is recognizable as a lighter line in the egg. On the third day you can see the small heart distinctly pulsating. Although the outline of the embryo from day to day becomes more distinct, shortly before hatching there is hardly any recognizable pigmentation to be seen. Only the eyes are clearly recognized as dark spots. How quickly the eggs develop is strongly dependent on temperature. At relatively high temperatures it is about six days until hatching. At 81o F it can take one day longer. You have to look closely to recognize that hatching has occurred. The yolk sack is about the same size as the original egg, and the unpigmented body of the fry is hard to see.
Ten days. Eleven days: feeding begins. Fourteen days.
The young of Ancistrus species usually use up their yolk sacks after about four days and then begin to eat. In H. zebra it takes considerably longer: 11-13 days until the enormous yolk sac has completely disappeared. After two days you can see the first signs of pigmentation; by the eighth day the young already exhibit the first signs of a zebra pattern. The intensity of the color is not strong, however. Only after two or three weeks do they take on intense black-and-white
coloration.
The Arndts have most recently found that in captivity very differently patterned zebra plecos are sometimes produced. One of their pairs suddenly produced four colorless young. The father already had a somewhat unusual caudal fin pattern; instead of a long band, this fish possessed elongate spots there. Three of the young strongly resembled L98 in their coloration at first. Later they colored up, however, and now have light coloration with a few irregular dark bands and some elongate spots. The forth animal is extremely light colored. Instead of the black pattern, it has a light gray one. Therefore, we have (just for fun) given it the name “ghost zebra.” It remains to be seen just how these aberrations arise. Are they genetic or environmental?
An apparent mutation: the “ghost zebra.”
This fish, with a slightly aberrant pattern, resembles L98.
It is assumed that the young of Hypancistrus zebra stay in the cave with the adult male until their yolk sacs are completely used up. This is the case with the related Ancistrus. I say that this is assumed, because I do not know whether it actually is so. At present, none of the breeders consulted by me swear that this is the case. The young were always already out of their brood cave when first seen. I do not believe, however, that this is normal, since in the wild, young with such a large yolk sac probably would not survive without parental protection.
Juvenile at two months old and a length of about an inch.
It also sometimes happens that the entire spawn or individual eggs get swirled out of the cave. Whether the adhesiveness of the eggs is connected with water chemistry, as is known of some other tropical fish eggs that lose their stickiness in hard water, must one day be clarified. The eggs of Hypancistrus zebra, however, can be raised artificially with a good degree of success, so that this is not quite so bad.
But even when the male looks after the eggs faithfully, some dangers may lurk for the eggs. Small snails can multiply so greatly that the male scarcely can win out against them. Planarians in the tank are far worse. Actually, when you notice the latter it often is already too late, since they hide during the day. Under cover of darkness they can destroy an entire spawn. Using chemicals against planarians often fails, as they can be quite resistant. It is often necessary to remove the fishes from the tank and sterilize everything.
Juvenile at four months.
The Rearing of the Yong Zebras
The rearing of the young presents no real problems. Since they are even larger than the fry of Ancistrus by the time they have absorbed their yolk sacs, the survival rate is high. They immediately take dried foods and fine frozen or live foods. I feed principally with brine shrimp nauplii and a mixture of various chopped dried foods, most of which contain Spirulina algae.
As with the rearing of all loricariids, cleanliness in the fry tank is vital. Uneaten food must be vacuumed up as quickly as possible, and frequent water changes are important. Their growth rate is quite slow, but continuous. After 2½ months they reach a size of about one inch.
Juvenile at six months.
Summary
To summarize in a few words, I can say that Hypancistrus zebra is a good aquarium fish and a very spawnable loricariid when following conditions are met: there are well conditioned breeders of both sexes available; feeding is generous and varied; suitable spawning caves are offered; above-average filtration ensures a good water quality and a high oxygen level; and the water temperature is at least 81o F. (Tropical Fish Hobbyist, Volume 44, Number 5, January 1996).
Literature Cited
Elsholz, K.D. and W. Elsholz. 1992. Erfolgreiche Zucht von Lasiancistrus scolymus. DATZ (Sonderheft “Harnichenwelse”).
Insbrucker, I.J.H. and H. Nijssen. 1991. Hypancistrus zebra, a new genus and species of uniquely pigmented ancistrine loricariid fish from the Rio Xingu, Brazil (Pisces: Siluriformes: Loricariidae). Ichthyol. Explor. Freshwaters, 1(4):345-350.
Pahnke, H. 1993. Seit zwei Jahren regelmassig gezuchtet: Hypancistrus zebra. DATZ, 42(4): 227-231.
Schliewen, U. and R. Stawikowski. 1989. Zebras aus Brasilien. DATZ, 42(9):521.
Stawikowski R. 1992. “Kaktusse,” “Russelzahn,” und ein merkwurdiges “Zebra.” DATZ, 45(6):348-349.
Steindachner, F. 1882. Beitrage zur Kenntnis der Flussfische Sudamerika’s II. Denkschr. Akad. Wiss. Wein. Math.-naturw. Cl. 43:103-146, 7pls.
Walter, O. 1993. Nachzucht gelungen: Hypancistrus zebra. DATZ, 46(10):633.
Since its original import in 1989, the zebra pleco has maintained the status of one of the most popular- and misunderstood- Loricariidae available. There have been several successful spawnings of this fish reported; however, even with an accurate article explaining the event, the most successful aquarists still have had very little success replicating them. There are several reasons for that, and neither the author nor the hobbyists are at fault.
After I read the article in the January 1996 issue of this magazine, I became convinced that I was going to jump on this ticket to fortune. It wasn't until after I had gotten my group of five of these fish that I found out that it was not going to be as easy as it looked in type. Although I followed every detail listed in the article to the letter, I was also unable to get a spawning. With my reputation at stake, I decided to start a more in-depth study of this amazing fish.
Coming from a fairly stable environment, zebra plecos are not
extremely tolerant of changes in water chemistry or
temperature.
I have always been a firm believer of duplicating the natural environment of a fish to get them to spawn, but the biotope seemed to vary depending on who you talked to. The only thing that everyone agreed upon was that the water was very soft. With that little bit of information, and a few books, I started reading about as many other fish as I could from the same region, searching for spawning successes of them all. After several weeks of that, I found out that I had taken on a fairly futile quest. At that point, I was ready to give up on the idea of ever raising my first fry of this species. Luckily, I already had a great deal of experience with spawning other members of this family, and that was where my success began.
The first pleco that I ever spawned was Peckoltia vittata. In most of the general books published, this fish is reported to come from the Amazon basin to the Rio Xingu. In a stroke of ignorance- I later found out that the group I had were from the Amazon- I assumed that this fish came from the same area. The only sensible thing to do was to try the same set of parameters.
Then on Christmas day, while I was setting up a new tank on the same stand, under theirs, I looked up and saw two half-inch fry. One of them was very unusual in that it didn't have the first stripe on it. However, it did have a gorgeous pure white body.
Over the last seven years, I have learned that several factors are important to spawning any
of the Loricariidae. I get a lot of questions about the "why" of my methods, and this fish is a perfect example of why I do most of them.
The first, and probably most important, step to success is maintaining very stable conditions in the spawning tank. There are several things which are tied into saying this. You have to constantly monitor temperature, pH, hardness, ammonia, nitrites, nitrates, and dissolved oxygen. Most aquarists are familiar with all of these parameters, and probably test all of them, except dissolved oxygen, on a regular basis. I believe the reason that people are not testing this is because a lack of understanding of exactly what it does.
Although it is necessary for respiration, it also acts as a chemical buffer against ammonia spikes. Ammonia can be found in two different forms, NH3 and NH4+. Both of these are involved in the nitrogen cycle. The problem at higher temperatures is that proteins form ammonia very quickly and there is not enough oxygen to maintain a large colony of the beneficial bacteria. By maintaining an excess of oxygen, it is not a problem for the bacteria to reproduce very rapidly and take care of any unusually high amounts of ammonia.
The natural habitat of the zebra pleco is one of huge currents-for which the
suckermouth is a definite advantage. To spawn these fish, you must attend to
the position and velocity of water currents in the aquarium.
It should be realized that a strong current is not always going to equal a high level of dissolved oxygen. My breeders are kept in a 29-gallon tank with 400 gallons per hour of filtration, and the oxygen levels still drop when I am too busy with my life to do water changes. It is possible to buy devices, sold as aquarium oxygenators, from pet shops. They may have to special order them, but they definitely make it easier if you have a busy schedule. If I have convinced anyone of the importance of oxygen, a proper level for this fish would be anything above 6.0 ppm. Oxygen will not stay in the water very long at the required temperature, so you may find yourself refilling the oxygenator very often.
As I mentioned earlier, stability is very important, so this may be a good time to explain an important detail of water changes. I use reverse osmosis water, and treat with trace elements to raise the Total Dissolved Solids to 90 ppm. This reading is not important, but is what I use on all of my softhingyer fishes. It keeps it simple, and all of them seem to do fine in it. The one thing that I have found that is important is the temperature of the water. For the aquarists who have never seen the Rio Xingu, I'll describe it. It's huge, about half a mile wide and 60 feet deep in some places. Therefore, in nature they are never going to get a sudden cold shock, and in an aquarium that will put a stop to any hopes of a spawning for several weeks. It is not necessary to put a heater in your mixing bucket, but at least allow the water to rise to room temperature. It is also much easier on the fish if 10 percent water changes are done daily rather than a large one weekly.
The other values should be very well known by every reader of this magazine, so it should suffice to say "keep it in check and you will get eggs." Yes, I said eggs. I have never had a male guard a fry to the point that the yolk sac was gone-about 11 days post hatch. The longest they have ever kept them was two days post hatch.
I do, however, have a theory about this situation. In the wild, these fish have been reported to live in the back part of Scobiancistrus aureatus, L14, or goldy pleco nests. After I was told about this, I figured that they were using the larger pleco to guard their fry. This is only a theory, and may be wrong, but it would explain why a fish which has the general shape of a marble with a needle laying on top of it is kicked out of the nest. In a heavily decorated tank, there will usually be survivors. However, if you happen to see any fry hiding in the rocks, by all means, separate them. The adults will make short work of them if they find them.
Back to the general chemistry of the water; my best successes have been at a pH of 6.0-6.5, a general hardness of less than 1 ppm, and a temperature of 86°F (30°C).
The eggs of H.zebra.
Feeding is another subject that should be discussed. There has been a lot of controversy about the nutritional requirements of these fish. Some people say they are vegetarian, and others insist that they are omnivores. I can sum this argument up in one sentence: They eat anything that you offer. Mine will spawn on two daily feedings of high protein spirulina flakes, but do not condition as fast as they could. In the past, I have also used bloodworms, blackworms, and brine shrimp. The females come into condition much quicker if they are offered the flakes along with a tray of blackworms kept in the tank. Protein is definitely a must, and they will not spawn without it.
Because of space limitations, I have found that it is possible to I keep a breeding group of these in the same tank. Each male should have a cave to call his own. The females are left to fend for themselves, and will try to enter the males' cave for no other reason than shelter. The male will not allow this unless the female is ripe, in which case they will spawn before he kicks her out.
A zebra pleco hatchling.
When a female is in good condition, this is one of the few plecos that will allow you to watch the courtship. The female will sit at the front of the cave and try to attract the male to the front. At this point, she will start swimming back and forth until she has managed to coax the male completely out of his cave, and will enter as soon as he leaves. This is when she lays her first batch of eggs. The male will then force her out of the nest to fertilize them and resume his position guarding the entrance, and she has to get him outside again to finish depleting her supply. I have also seen the female just swim into the cave without this ritual and have a successful spawn; however, it is not very common. I have never witnessed what goes on inside the caves, but have seen them up to this point. For the best results, you should give them till the next morning and remove the eggs to artificially hatch.
With the small amount of eggs- 15 is a huge spawn- it is very easy to hatch them. I use convalescent homes, the plastic box that shops use to net fish, hung in the parents tank. An airstone placed on the other side of the container will give enough circulation to keep any sediment from settling on the eggs. One very important factor is water changes in the container. These should be done at least twice daily, and more often after the fry are eating. The good news is, they are very large once the yoke sac is gone- just over a quarter inch and can eat brine shrimp nauplii almost as fast as you can put it in the tank. At about a month of age, the fry will be almost 3/4 inch and can be placed in the tank with their parents, but I prefer to transfer them to a 10-gallon tank of their own to grow out.
At this point, I would like to explain why I think this method works so well. The 400 gallons per hour of filtration is used to mimic the very strong currents in the natural river setting. It is very important that there are no calm areas on the surface, and a canister filter outfitted with a spray bar works very nicely for this. Also, because of the turbulent surface, gas exchange is increased greatly. One very important point that should be made is that the current should not be aimed directly at the spawning cave. This will cause the male to abandon the cave. I was asked about this recently and decided to experiment with it. It was several weeks before the male would go back to the site.
As for the number of caves, I believe I should give both sides of the story and let you decide. The Rio Xingu has been reported in the past to have an almost rift lake layout. This can easily be created in an aquarium by layering several rocks on top of each other. My original breeding set-up was done in this fashion, but it was a lot of trouble netting fry and the males could not establish any kind of territory because of the amount of openings in such a design.
Using a single cave per male is an adaptation of my usual pleco spawning tank. The only real difference is that with any other species I would only have one male per tank. This idea was taken by an article that I read in a scientific journal several years ago. As explained in the article, most Loricariidae will spawn year-round in nature. The only factor that prevents this is the number of available nesting sites. It also had a great deal of information about how to place the caves to make them breeding caves, and not just decorations. The opening of the cave should be placed opposite the water flow and the back should be completely sealed. After seeing the benefits of this, it is almost self explanatory. The back of the cave is where the eggs are laid, probably for defense reasons, and the strong current would cause them to be battered fiercely.
With this same principle in mind, this may be a good time to explain what I believe is the best way to get accurate chemical parameters for spawning. Several conservationist groups give grants every year to ecologists for limnology research. They get vital information about natural rivers and lakes which they can use in allocating funds for wildlife reserves and other things. The point is, by collecting this information through their publications or on the Internet, we can become aware of the water chemistry of our fishes' natural habitat during that time of the year. By using that small amount of knowledge, combined with the information that plecos will spawn year-round in their natural habitat, it should stand to reason that they will spawn in that water.
Length = Length of the fish;
Width = Body width + 2/3 of the length of the pectoral fin;
Height = Height of the body + 2/3 of the height of the dorsal fin.
If you want to spare yourself the measurement of your fish, you can use the measurements of 3.5 x 1.0 x 0.6 inches (L x W x H) for a cave to accommodate full-grown fish. For younger fish you should select accordingly smaller caves. Most other loricariids also accept these caves very well.
Eventually, the location of the cave also is of importance. Rickhoff made the observation that his zebras mostly received a strong current from the filter. Perhaps the caves were selected so that the eggs and young get the optimum amount of fresh water and oxygen. This is only a supposition, but one that tallies completely with my observations.
A male in one of the specially constructed breeding caves.
Spawning
As a rule, the caves are accepted by the fish soon after they are placed in the tank. In a broad sense, the spawning of Hypancistrus resembles that of the bristlenose plecos of the genus Ancistrus, but there are differences. Whereas spawning readiness in Ancistrus males is announced by wagging with the paired fins in front of the cave, Hypancistrus males exhibit little activity beforehand. You will simple notice all of a sudden that the fish have paired off.
According to Karin & Gerd Arndt, the egglaying behavior resembles very strongly that of Ancistrus species. The zebras often lay on top of each other in the cave. Finally, the male lays sideways with his caudal fin and half of his body on the head of the female. She produces her eggs in several batches. The male blocks the cave entrance with his head. After each group of eggs is laid, the female makes fidgety forward and backward movements to signal to the male that the eggs can now be fertilized. Since the female often will not leave the cave after spawning is over, she occasionally must be pushed out by the male.
The eggs are deposited in the slate cave mostly in the outermost corner, on the bottom. Whether the males mouth the eggs, as in Ancistrus, has not yet been observed. The fanning movements with the pelvic fins are sporadic. When “danger” threatens (for example, when a flashlight is shined into the cave) the male covers the egg mass almost completely, so that at most only one to two eggs can be seen.
The Arndts’s zebra plecos spawned on 10 June 1994 for the first time. Unfortunately, they had little luck, since on 13 June the empty eggshells lay in front of the cave. Probably this spawn was not fertilized. There was no basis for worry, however, since in other loricariids there are many cases in which the first spawn in not fertilized.
The second spawn went better. The eggs were laid on the evening of 13 June. In spite of frequent inspections the next day, the exact number could not be determined. On 18 June, six fry with enormous yolk sacks were sighted outside of the cave and were siphoned out. The fry were transferred to a net-covered breeder box hung inside the tank in the filter current. Unfortunately, three of the young died after a short time. On 23 June the male once more was seen sitting on a spawn, and on 24 June a second male in another hole did the same. Since then the Arndts have had their zebras producing pretty regularly.
As I mentioned earlier, the spawning of my H. zebra happened very unexpectedly. I kept three fish for than two years, but in the end they reached a size of about 3.6 inches and all were obviously males. Therefore, I expanded my H. zebra stock in the late summer of last year with about five additional fish, all of which were smaller. After their quarantine I still did not place them with the full-grown males, since to me they simply appeared much too small to be able to spawn with them. So, I placed them in a 75-gallon tank for grow-out, along with five large Pseudohemiodon laticeps and some Ancistrus sp. Apart from some plants in clay pots and some slate, there were only two of the specially made spawning caves. The zebra plecos hid mostly under the slate or behind the filter. After several months, however, the largest specimen, a male, had reached a size of 2.6 inches and showed interest in the cave. It even selected the larger of the two caves, manageing to chase away the larger Ancistrus. After two days, a somewhat smaller zebra was staying near the male. Obviously this was a female. Soon, she entered the cave with the male. I could not quite believe that the fish were spawning at this small size, and so the next day I turned the cave somewhat in order to be able to light it for photography. The frightened male performed some jerky movements, and to my total shock, 12 eggs were dislodged from the cave.
Since I had had previous experience with artificial rearing of other loricariids, I had no great concern about the eggs. I transferred them carefully into a small Plexiglas tank that was filled with aged fresh water. In order to maintain the proper temperature, it was simply hung in the adults’ tank. An airstone provided the necessary oxygen supply. For prevention of fungus I added acriflavine. After a day, it was apparent that two eggs were bad. I prodded these eggs with a pipette and sucked the contents out completely so that only the shells remained. This measure is necessary because the eggs stick so strongly together that the bad eggs cannot be separated without risking damage to the good ones. Afterward I did a complete water change in the brooder box. After four days it could be seen that another egg showed no development. This egg was also siphoned out. At 86oF, nine fry hatched on the seventh day. In a second spawn, about four weeks later, my artificial rearing was more successful; I managed to get 11 fry out of 12 eggs.
Development of Eggs and Young
In nearly all of the ancistrine loricariids that have been spawned to date, the eggs are yellow in color. When you see the eggs of the zebra pleco for the first time, on the basis of their milky white coloration you would think that they were infertile. The size of the eggs also is a curiosity. The egg diameter, according to the age and feeding condition of the female, can vary between 4 and 5 mm. Interestingly, larger loricariids, such as the Ancistrus species or Lasiancistrus scolymus (see Elsholz & Elsholz, 1992), usually have smaller eggs. Accordingly, however, the number of eggs is small. In past broods the number varied between 7 and 12 eggs. I expect, however, that fully grown females that are well fed might be able to lay up to 20 eggs.
Seven days. Eight days. Nine days.
Immediately after they are laid, hardly any structures are recognizably in the interior of these eggs. After one day, however, the body of the embryo is recognizable as a lighter line in the egg. On the third day you can see the small heart distinctly pulsating. Although the outline of the embryo from day to day becomes more distinct, shortly before hatching there is hardly any recognizable pigmentation to be seen. Only the eyes are clearly recognized as dark spots. How quickly the eggs develop is strongly dependent on temperature. At relatively high temperatures it is about six days until hatching. At 81o F it can take one day longer. You have to look closely to recognize that hatching has occurred. The yolk sack is about the same size as the original egg, and the unpigmented body of the fry is hard to see.
Ten days. Eleven days: feeding begins. Fourteen days.
The young of Ancistrus species usually use up their yolk sacks after about four days and then begin to eat. In H. zebra it takes considerably longer: 11-13 days until the enormous yolk sac has completely disappeared. After two days you can see the first signs of pigmentation; by the eighth day the young already exhibit the first signs of a zebra pattern. The intensity of the color is not strong, however. Only after two or three weeks do they take on intense black-and-white
coloration.
The Arndts have most recently found that in captivity very differently patterned zebra plecos are sometimes produced. One of their pairs suddenly produced four colorless young. The father already had a somewhat unusual caudal fin pattern; instead of a long band, this fish possessed elongate spots there. Three of the young strongly resembled L98 in their coloration at first. Later they colored up, however, and now have light coloration with a few irregular dark bands and some elongate spots. The forth animal is extremely light colored. Instead of the black pattern, it has a light gray one. Therefore, we have (just for fun) given it the name “ghost zebra.” It remains to be seen just how these aberrations arise. Are they genetic or environmental?
An apparent mutation: the “ghost zebra.”
This fish, with a slightly aberrant pattern, resembles L98.
It is assumed that the young of Hypancistrus zebra stay in the cave with the adult male until their yolk sacs are completely used up. This is the case with the related Ancistrus. I say that this is assumed, because I do not know whether it actually is so. At present, none of the breeders consulted by me swear that this is the case. The young were always already out of their brood cave when first seen. I do not believe, however, that this is normal, since in the wild, young with such a large yolk sac probably would not survive without parental protection.
Juvenile at two months old and a length of about an inch.
It also sometimes happens that the entire spawn or individual eggs get swirled out of the cave. Whether the adhesiveness of the eggs is connected with water chemistry, as is known of some other tropical fish eggs that lose their stickiness in hard water, must one day be clarified. The eggs of Hypancistrus zebra, however, can be raised artificially with a good degree of success, so that this is not quite so bad.
But even when the male looks after the eggs faithfully, some dangers may lurk for the eggs. Small snails can multiply so greatly that the male scarcely can win out against them. Planarians in the tank are far worse. Actually, when you notice the latter it often is already too late, since they hide during the day. Under cover of darkness they can destroy an entire spawn. Using chemicals against planarians often fails, as they can be quite resistant. It is often necessary to remove the fishes from the tank and sterilize everything.
Juvenile at four months.
The Rearing of the Yong Zebras
The rearing of the young presents no real problems. Since they are even larger than the fry of Ancistrus by the time they have absorbed their yolk sacs, the survival rate is high. They immediately take dried foods and fine frozen or live foods. I feed principally with brine shrimp nauplii and a mixture of various chopped dried foods, most of which contain Spirulina algae.
As with the rearing of all loricariids, cleanliness in the fry tank is vital. Uneaten food must be vacuumed up as quickly as possible, and frequent water changes are important. Their growth rate is quite slow, but continuous. After 2½ months they reach a size of about one inch.
Juvenile at six months.
Summary
To summarize in a few words, I can say that Hypancistrus zebra is a good aquarium fish and a very spawnable loricariid when following conditions are met: there are well conditioned breeders of both sexes available; feeding is generous and varied; suitable spawning caves are offered; above-average filtration ensures a good water quality and a high oxygen level; and the water temperature is at least 81o F. (Tropical Fish Hobbyist, Volume 44, Number 5, January 1996).
Literature Cited
Elsholz, K.D. and W. Elsholz. 1992. Erfolgreiche Zucht von Lasiancistrus scolymus. DATZ (Sonderheft “Harnichenwelse”).
Insbrucker, I.J.H. and H. Nijssen. 1991. Hypancistrus zebra, a new genus and species of uniquely pigmented ancistrine loricariid fish from the Rio Xingu, Brazil (Pisces: Siluriformes: Loricariidae). Ichthyol. Explor. Freshwaters, 1(4):345-350.
Pahnke, H. 1993. Seit zwei Jahren regelmassig gezuchtet: Hypancistrus zebra. DATZ, 42(4): 227-231.
Schliewen, U. and R. Stawikowski. 1989. Zebras aus Brasilien. DATZ, 42(9):521.
Stawikowski R. 1992. “Kaktusse,” “Russelzahn,” und ein merkwurdiges “Zebra.” DATZ, 45(6):348-349.
Steindachner, F. 1882. Beitrage zur Kenntnis der Flussfische Sudamerika’s II. Denkschr. Akad. Wiss. Wein. Math.-naturw. Cl. 43:103-146, 7pls.
Walter, O. 1993. Nachzucht gelungen: Hypancistrus zebra. DATZ, 46(10):633.
Since its original import in 1989, the zebra pleco has maintained the status of one of the most popular- and misunderstood- Loricariidae available. There have been several successful spawnings of this fish reported; however, even with an accurate article explaining the event, the most successful aquarists still have had very little success replicating them. There are several reasons for that, and neither the author nor the hobbyists are at fault.
After I read the article in the January 1996 issue of this magazine, I became convinced that I was going to jump on this ticket to fortune. It wasn't until after I had gotten my group of five of these fish that I found out that it was not going to be as easy as it looked in type. Although I followed every detail listed in the article to the letter, I was also unable to get a spawning. With my reputation at stake, I decided to start a more in-depth study of this amazing fish.
Coming from a fairly stable environment, zebra plecos are not
extremely tolerant of changes in water chemistry or
temperature.
I have always been a firm believer of duplicating the natural environment of a fish to get them to spawn, but the biotope seemed to vary depending on who you talked to. The only thing that everyone agreed upon was that the water was very soft. With that little bit of information, and a few books, I started reading about as many other fish as I could from the same region, searching for spawning successes of them all. After several weeks of that, I found out that I had taken on a fairly futile quest. At that point, I was ready to give up on the idea of ever raising my first fry of this species. Luckily, I already had a great deal of experience with spawning other members of this family, and that was where my success began.
The first pleco that I ever spawned was Peckoltia vittata. In most of the general books published, this fish is reported to come from the Amazon basin to the Rio Xingu. In a stroke of ignorance- I later found out that the group I had were from the Amazon- I assumed that this fish came from the same area. The only sensible thing to do was to try the same set of parameters.
Then on Christmas day, while I was setting up a new tank on the same stand, under theirs, I looked up and saw two half-inch fry. One of them was very unusual in that it didn't have the first stripe on it. However, it did have a gorgeous pure white body.
Over the last seven years, I have learned that several factors are important to spawning any
of the Loricariidae. I get a lot of questions about the "why" of my methods, and this fish is a perfect example of why I do most of them.
The first, and probably most important, step to success is maintaining very stable conditions in the spawning tank. There are several things which are tied into saying this. You have to constantly monitor temperature, pH, hardness, ammonia, nitrites, nitrates, and dissolved oxygen. Most aquarists are familiar with all of these parameters, and probably test all of them, except dissolved oxygen, on a regular basis. I believe the reason that people are not testing this is because a lack of understanding of exactly what it does.
Although it is necessary for respiration, it also acts as a chemical buffer against ammonia spikes. Ammonia can be found in two different forms, NH3 and NH4+. Both of these are involved in the nitrogen cycle. The problem at higher temperatures is that proteins form ammonia very quickly and there is not enough oxygen to maintain a large colony of the beneficial bacteria. By maintaining an excess of oxygen, it is not a problem for the bacteria to reproduce very rapidly and take care of any unusually high amounts of ammonia.
The natural habitat of the zebra pleco is one of huge currents-for which the
suckermouth is a definite advantage. To spawn these fish, you must attend to
the position and velocity of water currents in the aquarium.
It should be realized that a strong current is not always going to equal a high level of dissolved oxygen. My breeders are kept in a 29-gallon tank with 400 gallons per hour of filtration, and the oxygen levels still drop when I am too busy with my life to do water changes. It is possible to buy devices, sold as aquarium oxygenators, from pet shops. They may have to special order them, but they definitely make it easier if you have a busy schedule. If I have convinced anyone of the importance of oxygen, a proper level for this fish would be anything above 6.0 ppm. Oxygen will not stay in the water very long at the required temperature, so you may find yourself refilling the oxygenator very often.
As I mentioned earlier, stability is very important, so this may be a good time to explain an important detail of water changes. I use reverse osmosis water, and treat with trace elements to raise the Total Dissolved Solids to 90 ppm. This reading is not important, but is what I use on all of my softhingyer fishes. It keeps it simple, and all of them seem to do fine in it. The one thing that I have found that is important is the temperature of the water. For the aquarists who have never seen the Rio Xingu, I'll describe it. It's huge, about half a mile wide and 60 feet deep in some places. Therefore, in nature they are never going to get a sudden cold shock, and in an aquarium that will put a stop to any hopes of a spawning for several weeks. It is not necessary to put a heater in your mixing bucket, but at least allow the water to rise to room temperature. It is also much easier on the fish if 10 percent water changes are done daily rather than a large one weekly.
The other values should be very well known by every reader of this magazine, so it should suffice to say "keep it in check and you will get eggs." Yes, I said eggs. I have never had a male guard a fry to the point that the yolk sac was gone-about 11 days post hatch. The longest they have ever kept them was two days post hatch.
I do, however, have a theory about this situation. In the wild, these fish have been reported to live in the back part of Scobiancistrus aureatus, L14, or goldy pleco nests. After I was told about this, I figured that they were using the larger pleco to guard their fry. This is only a theory, and may be wrong, but it would explain why a fish which has the general shape of a marble with a needle laying on top of it is kicked out of the nest. In a heavily decorated tank, there will usually be survivors. However, if you happen to see any fry hiding in the rocks, by all means, separate them. The adults will make short work of them if they find them.
Back to the general chemistry of the water; my best successes have been at a pH of 6.0-6.5, a general hardness of less than 1 ppm, and a temperature of 86°F (30°C).
The eggs of H.zebra.
Feeding is another subject that should be discussed. There has been a lot of controversy about the nutritional requirements of these fish. Some people say they are vegetarian, and others insist that they are omnivores. I can sum this argument up in one sentence: They eat anything that you offer. Mine will spawn on two daily feedings of high protein spirulina flakes, but do not condition as fast as they could. In the past, I have also used bloodworms, blackworms, and brine shrimp. The females come into condition much quicker if they are offered the flakes along with a tray of blackworms kept in the tank. Protein is definitely a must, and they will not spawn without it.
Because of space limitations, I have found that it is possible to I keep a breeding group of these in the same tank. Each male should have a cave to call his own. The females are left to fend for themselves, and will try to enter the males' cave for no other reason than shelter. The male will not allow this unless the female is ripe, in which case they will spawn before he kicks her out.
A zebra pleco hatchling.
When a female is in good condition, this is one of the few plecos that will allow you to watch the courtship. The female will sit at the front of the cave and try to attract the male to the front. At this point, she will start swimming back and forth until she has managed to coax the male completely out of his cave, and will enter as soon as he leaves. This is when she lays her first batch of eggs. The male will then force her out of the nest to fertilize them and resume his position guarding the entrance, and she has to get him outside again to finish depleting her supply. I have also seen the female just swim into the cave without this ritual and have a successful spawn; however, it is not very common. I have never witnessed what goes on inside the caves, but have seen them up to this point. For the best results, you should give them till the next morning and remove the eggs to artificially hatch.
With the small amount of eggs- 15 is a huge spawn- it is very easy to hatch them. I use convalescent homes, the plastic box that shops use to net fish, hung in the parents tank. An airstone placed on the other side of the container will give enough circulation to keep any sediment from settling on the eggs. One very important factor is water changes in the container. These should be done at least twice daily, and more often after the fry are eating. The good news is, they are very large once the yoke sac is gone- just over a quarter inch and can eat brine shrimp nauplii almost as fast as you can put it in the tank. At about a month of age, the fry will be almost 3/4 inch and can be placed in the tank with their parents, but I prefer to transfer them to a 10-gallon tank of their own to grow out.
At this point, I would like to explain why I think this method works so well. The 400 gallons per hour of filtration is used to mimic the very strong currents in the natural river setting. It is very important that there are no calm areas on the surface, and a canister filter outfitted with a spray bar works very nicely for this. Also, because of the turbulent surface, gas exchange is increased greatly. One very important point that should be made is that the current should not be aimed directly at the spawning cave. This will cause the male to abandon the cave. I was asked about this recently and decided to experiment with it. It was several weeks before the male would go back to the site.
As for the number of caves, I believe I should give both sides of the story and let you decide. The Rio Xingu has been reported in the past to have an almost rift lake layout. This can easily be created in an aquarium by layering several rocks on top of each other. My original breeding set-up was done in this fashion, but it was a lot of trouble netting fry and the males could not establish any kind of territory because of the amount of openings in such a design.
Using a single cave per male is an adaptation of my usual pleco spawning tank. The only real difference is that with any other species I would only have one male per tank. This idea was taken by an article that I read in a scientific journal several years ago. As explained in the article, most Loricariidae will spawn year-round in nature. The only factor that prevents this is the number of available nesting sites. It also had a great deal of information about how to place the caves to make them breeding caves, and not just decorations. The opening of the cave should be placed opposite the water flow and the back should be completely sealed. After seeing the benefits of this, it is almost self explanatory. The back of the cave is where the eggs are laid, probably for defense reasons, and the strong current would cause them to be battered fiercely.
With this same principle in mind, this may be a good time to explain what I believe is the best way to get accurate chemical parameters for spawning. Several conservationist groups give grants every year to ecologists for limnology research. They get vital information about natural rivers and lakes which they can use in allocating funds for wildlife reserves and other things. The point is, by collecting this information through their publications or on the Internet, we can become aware of the water chemistry of our fishes' natural habitat during that time of the year. By using that small amount of knowledge, combined with the information that plecos will spawn year-round in their natural habitat, it should stand to reason that they will spawn in that water.