Bugs and moss. I think you'll be fine if you let him swim around the lake for a few hours every day though! He's already got the water squirting down pat, and there's plenty of mossy rocks under the water.

[Right? Yeah.]

You should probably find a pretty big aquarium to put him in to -- I can help. They like living in coral in the wild, and keeping him hydrated's going to be your biggest concern.