I wasn't able to post till now. I just don't want another teacher to read this then think, "Hey, that's a great idea!". Then grab an aquarium and some decorations and break his/her kids hearts when a lot of fish die off. Minus the teacher part that's what happened to me. But by goodness I learned my lesson. If I can prevent that from happening to anyone else's kids (I know I can't) then I will try.
I think you have a great idea tho.