Post by MADMIKE on Mar 22, 2007 14:05:31 GMT -5
www.hallman.org/plant/gravel.html
Gravel/Substrate
By Jim Kelly
This is one of the most important items to consider for healthy plant growth. I have gotten absolutely superior growth (after having tried many other substrates with much less success) from the following formula. There are two layers:
For the bottom layer mix potting vermiculite (from any nursury) with enough water to wet the vermiculite well but not so much that it floats. Squeeze and knead the vermiculite to get as much air out of it as possible, and also to separate the different layers of the vermiculite granules, making the mixture as fine as possible. When your hands look like they're covered in gold dust, you're done. Now add some soil that you have dug from outside (garden topsoil). See the suggestions for soils at the end of this section.
You should mix in enough of this to turn the vermiculite from its shimmery golden color to grey. For example, I used about two gallons of Yolo loam with enough vermiculite to make a 3-inch layer in a 55 gallon tank, or about a quart mixed with enough vermiculite to make a 1.5-inch layer in a 10 gallon tank. The precise amounts are not important. After mixing in the soil, the mixture should no longer be runny with water. If it is, your tank will be quite cloudy when you add the water to fill it, so add more soil and vermiculite until it is no longer runny with water, but comparable to prepared cake mix before you cook it. This bottom layer forms a rich, soft medium for roots to penetrate into and obtain nutrients from. This layer should be as thick as possible, within aesthetic limits.
The top layer is simply sand. You need about a 1 inch or more layer, simply to keep the lower layer from clouding the water. The best is #3 sandblasting grit, which our local gravel yard sells in 100 lb. bags for $10. Any sand that is not from the sea and is not too fine will do. #3 sand is about 2 mm in diameter. Just pour it on top, and level it out. Wash it first if you think it needs it. This layer should be at least 1" thick, and not more than 2".
Now you can carefully add the water to the tank. Put down some paper or something flat at the bottom of the tank to keep the soil from being stirred up while you add the water. If you are careful, the water will be crystal clear when you finish. If you stirred up the soil by accident, it will take 2-5 days to clear up, so be patient. A small puff of soil will come up when you uproot a plant, but does not present a problem. After you have planted the plants, you can add a small amount of solid fertilizer to the bottom layer of the substrate (see the fertilizer section).
For those interested in what to look for in a soil that will grow aquatic plants well, here is additional info. Don't use bagged potting soil, peat moss, or compost (They will decay under water and prevent good root growth. See the recent article by Diane Walstad in the Sept. 1994 issue of TAG. They offer a short-term supply of nutrients which will have to be replenished with solid fertilizer eventually anyway, so you might as well just use a solid fertilizer from the beginning and avoid the problems associated with decaying organic matter, such as hydrogen sulfide formation.) Try to find a soil low in organic matter and high in fine clay particles. It should not be sandy soil or very firm, fine clay either, but somewhere in the middle.
Sand has insufficient cation exchange capacity and is too coarse to contact the roots on their entire surface area. These are the two most important factors which influence how well roots can obtain nutrient ions from the soil. Very fine clay (close to Play-Doh texture) might cloud the water when you uproot plants in the aquarium. If you are a student, you might want to go to the university library and look up the types of soils in your area and their properties in government soil survey books which usually have maps telling you where to find the different soils, as well as important chemical properties. You want a soil that has a high cation exchange capacity and low organic matter content, and has metal ions which are present in only moderate quantities (too much can be toxic to plants). I have used "Yolo loam" from the UC Davis campus with great success in my home tanks. It was not chosen specially, but it is just what is available locally. Here is the analysis:
Yolo Loam (from Yolo county, CA)
% sand (2mm to 0.05mm) 28.7%
% silt (50 microns to 2 microns) 46.4%
% clay (< 2 microns) 24.9% pH 6.7
% carbonates (not tested)
phosphorus in soil 12.5 ppm
Fe as Fe2O3 (not tested)
Ca 10.5 me/100g Mg 10.8 me/100g
Na 0.3 me/100g
K 0.1 me/100g
cation exchange capacity 26.5 me/100g
% base saturation 81.9
% organic carbon 1.38%
% organic nitrogen 0.125%
Gravel/Substrate
By Jim Kelly
This is one of the most important items to consider for healthy plant growth. I have gotten absolutely superior growth (after having tried many other substrates with much less success) from the following formula. There are two layers:
For the bottom layer mix potting vermiculite (from any nursury) with enough water to wet the vermiculite well but not so much that it floats. Squeeze and knead the vermiculite to get as much air out of it as possible, and also to separate the different layers of the vermiculite granules, making the mixture as fine as possible. When your hands look like they're covered in gold dust, you're done. Now add some soil that you have dug from outside (garden topsoil). See the suggestions for soils at the end of this section.
You should mix in enough of this to turn the vermiculite from its shimmery golden color to grey. For example, I used about two gallons of Yolo loam with enough vermiculite to make a 3-inch layer in a 55 gallon tank, or about a quart mixed with enough vermiculite to make a 1.5-inch layer in a 10 gallon tank. The precise amounts are not important. After mixing in the soil, the mixture should no longer be runny with water. If it is, your tank will be quite cloudy when you add the water to fill it, so add more soil and vermiculite until it is no longer runny with water, but comparable to prepared cake mix before you cook it. This bottom layer forms a rich, soft medium for roots to penetrate into and obtain nutrients from. This layer should be as thick as possible, within aesthetic limits.
The top layer is simply sand. You need about a 1 inch or more layer, simply to keep the lower layer from clouding the water. The best is #3 sandblasting grit, which our local gravel yard sells in 100 lb. bags for $10. Any sand that is not from the sea and is not too fine will do. #3 sand is about 2 mm in diameter. Just pour it on top, and level it out. Wash it first if you think it needs it. This layer should be at least 1" thick, and not more than 2".
Now you can carefully add the water to the tank. Put down some paper or something flat at the bottom of the tank to keep the soil from being stirred up while you add the water. If you are careful, the water will be crystal clear when you finish. If you stirred up the soil by accident, it will take 2-5 days to clear up, so be patient. A small puff of soil will come up when you uproot a plant, but does not present a problem. After you have planted the plants, you can add a small amount of solid fertilizer to the bottom layer of the substrate (see the fertilizer section).
For those interested in what to look for in a soil that will grow aquatic plants well, here is additional info. Don't use bagged potting soil, peat moss, or compost (They will decay under water and prevent good root growth. See the recent article by Diane Walstad in the Sept. 1994 issue of TAG. They offer a short-term supply of nutrients which will have to be replenished with solid fertilizer eventually anyway, so you might as well just use a solid fertilizer from the beginning and avoid the problems associated with decaying organic matter, such as hydrogen sulfide formation.) Try to find a soil low in organic matter and high in fine clay particles. It should not be sandy soil or very firm, fine clay either, but somewhere in the middle.
Sand has insufficient cation exchange capacity and is too coarse to contact the roots on their entire surface area. These are the two most important factors which influence how well roots can obtain nutrient ions from the soil. Very fine clay (close to Play-Doh texture) might cloud the water when you uproot plants in the aquarium. If you are a student, you might want to go to the university library and look up the types of soils in your area and their properties in government soil survey books which usually have maps telling you where to find the different soils, as well as important chemical properties. You want a soil that has a high cation exchange capacity and low organic matter content, and has metal ions which are present in only moderate quantities (too much can be toxic to plants). I have used "Yolo loam" from the UC Davis campus with great success in my home tanks. It was not chosen specially, but it is just what is available locally. Here is the analysis:
Yolo Loam (from Yolo county, CA)
% sand (2mm to 0.05mm) 28.7%
% silt (50 microns to 2 microns) 46.4%
% clay (< 2 microns) 24.9% pH 6.7
% carbonates (not tested)
phosphorus in soil 12.5 ppm
Fe as Fe2O3 (not tested)
Ca 10.5 me/100g Mg 10.8 me/100g
Na 0.3 me/100g
K 0.1 me/100g
cation exchange capacity 26.5 me/100g
% base saturation 81.9
% organic carbon 1.38%
% organic nitrogen 0.125%