I have a new shopping list and will probably keep the bigger snails in the smaller tank and just see how they go. The aquarium shop where we got them just called them "snails.". Two are white and one is black. They gave us the small one for free. I'm trying not to be annoyed that they didn't tell us whether it was a good idea or not to have them.
And also glad to know that I can do something about the ammonia in my tap water.
About the bio wheel... Was thinking of getting the marineland crescent 5 gallon with the LED lights. Is this the one you have? Good?