well, that took longer then i expected. sorry about that. i feel bad, but anyway heres the update. hes had 3 different rooms, one for saltwater, one for freshwater, and one for live foods. Hes had these algae tanks to grow algae in, for food. he has a couple tanks of brown algae, green algae, other algaes, etc. anyway, he actually has one for cyanobacteria, for tadpoles that eat them, like spring peeper tadpoles. anyway, things got out of hand when he went away for a week. he returned to see his 29 gallon green algae growing tank a mess... there was a crusty kind of algae growth on his walls. it wont come off, even with a razor. but thats not the worst. a corner of his tank had a snail like shell of algae. like 2 inches of a bumpy, hard, unbreakable algae. he pulled it out, and cant even dent it. i found out because i came up to his house to get some dried algae. i have no idea what it is, and hes pressure washing the 29 gallon, and first he sanded it with sandpaper. its coming off, but i just wanted to know if you know what this shell is. thanks!