well, let me clarify a bit.
I suggested it's OK to use in a "pot" in an aquarium, as you put it "potting soil" ... i've also used it as the tank's substrate, but that is not something I'd recommend for someone starting out, as it requires a LOT of patience waiting for the water to clear 8O
additionally, be sure to rinse well and cover with at least an inch of plain gravel.
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other products to look at:
Schultz Aquatic Potting Soil - walmart outdoor department
Seachem Flourite - several varieties, including a dark gray/black sand - found at some ma-n-pa pet stores as well as online
1st Layer Pure Laterite - gravel enchancer, available at most chain pet stores
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if I had to rank those in order of difficulty of use, the list would look like this, starting with most difficult
1. kitty litter
2. flourite
3. laterite
4. schultz