I have had a native tank set up as a gravel raceway and pool. I kept darter, scalpins, various minnows, fundulas killies and at one point some dollar sunfish fry less than an inch long. The sun fish grew rapidly, so back to nature they went. They were hell on aquascaping as well. The rest were very interesting to watch. My biggest problem, for most it would be a died and went to heaven positive, is I have a fishroom heated to 78 degrees. That is a tad warm for the stream fish and most natives from the midwest. I think maybe I'll give it a try at work.