(refrains from obvious joke).
I'm looking at a 40gallon breeder myself, because I love the large surface area and depth of the tank. The *perfect* tank for some bottom-dwellers, wouldn't you say? Let's see if my vision will do for you.
15 Kuhlie Loaches
5 Weather Loaches
5 Chinese Algae Eaters (I know, I know, but I love them)
15 Brilliant Rasboras
This steaming mixture all under a layer of duckweed. Toss a PC light over the duckweed and you can reduce water-changes to every 3 weeks or so, depending on growth.