im not sure. they seem to go around appearing to clean the walls. should i still get a snail?? (10gal w/ 4 fish. 1 blue gourami, 1 rainbow shark 1 red flame gourami and 1 black skirt tetra.) its not crowded i know what you are thinking. i have a really good top of the line filter and i have had fish for quite sometime. i have had these fish for a long time and they have been fine all along