Sounds like my footprint may not be ideal for something like that but I'll do some researchAs far as shell dwellers, you could do a pair of N. Multifasciatus if you got the lake cichlid water hardener. They do frequently a lot though, in my experience. I have had a continuous colony for several years and they are fun. They much prefer length over depth, though, so the top half of the tank would be mostly ignored by them, ad they couldn't handle tank mates there.