In with my RES and my musk i keep some amphipods (calleds skuds sometimes I think), they live and reproduce down in the aquarium gravel I use and you would need to keep them alive. Hopefully some who knows more will say something if there are risks that I am not aware of, such as parasites, which I know can be a problem with amphipods and fish. I got mine from a nearby river and they did noticable improve how often I had to change the filter.

oh well, hopefully this can be of some help, and I wouldent bother with plants haveing so many turtles to tear them up.

good luck with that.