I have pool filter sand in my 29 and 55 gallon tanks, I have very little in my 55 and would like to add even more to my 29 gallon also. I will be getting some MTS snails in a week or so, so I was curious if I could add some to my 55 gallon with 5 yo yo loaches, my 29 has only 2 small angelfish and a few other small fish. I've read where even the loaches have a hard time eating these snails. In my 55 gallon the sand has a green film over it at times and I'm sure that an addition of some of these snails would help alot, I'm also getting these snails for my multi (shell dweller) tank. If I don't add the extra sand to my 55 gallon I will probably just go ahead and remove the sand and replace it with gravel, the sand is so thin that the bottom of the tank shows through in alot of places.