I have these snail like creatures in my tank. Not just a few, but thousands. At times they attach themselves to the glass. It seems as if the whole substrate is moving. I have added two red tailed botias to eat some of them; they are just getting fat and not making a dent. Are there any tricks to get rid of them? I have thought of getting rid of the substrate and replacing it to kill most of them. I thought this would give the botias a chance to catch up. However, this seams like a lot of work. Any other ideas?