Mainly all epoxy paint are fish safe, but u have to wash it first and sun dried it before using.
Pls test the water with some small fishes before introducing your precious collection.
+1 on the krylon. One thing it is designed for plastic but if you are going to spray pvc you may want to scuff sand it first with some fine grit paper. It will double the adhesion. I sprayed some and in a couple months it was chipping off.