The bowfin is really cool. What size tank is that, is it big enough to add a gar? Very prehistoric and do pretty well with polys and bowfin from what I understand.
I was thinking of adding one of those 3d backgrounds but their really expensive, I finally found someplace that has them so if I ever decide to at least I've got a source. I like the background you've got though.
Just go with the good old black background. It never fails to make a tank look better.
Either that or paint it dark blue like i have. I only went with blue instead of black because i`ve got black sand and didn`t want the tank to look like a hole in the wall.. lol
But if we called the tank primitive, wouldn't it need to be made out of organic material, perhaps reeds and sticks, wound together, and placed in the river to keep the fish fresh and alive?