Pete: If you find the right snails, you will be happier with them. THat is why I am looking specifically for Venezualan ramshorns. They seem to tolerate the acidity of Amazon conditions without their shells beiung eaten, as well as reproducing very slowly, and being quite attractive. I have a phosphate problem in my water that seems to be endemic to the area I live. Any less light, and my sag and swords will begin to languish. I bought some phos-zorb, but it appears to only come packaged for pond use. Bob