I'm a little confused by this thread, as you start out by saying you want the temp to be around 78oF. If so, you would have to be careful in selecting your natives. Most will need lower temps, if only for a winter rest period. Darters are great, but some have fairly specific requirements. I kept some years ago when I lived in Virginia - the tank had lots of flow, and I kept it in the basement (which was unheated) so I could allow the temp to drop in the winter. The biggest problem I had was down to me keeping the darters with a range of native shiners and minnows - very little food made it to the bottom, so I more-or-less had to hand feed the darters individually. In any case, I'd suggest careful research before you launch into keeping darters.
Tony