How about a couple of German Blue or Gold Rams? Also, the poster that mentioned various smaller pleco species is right on (clowns, L 201s, L 204, BN - personally). Consider Banjo cats as well. And various driftwood cat species, such as C. Perugaie. I've personally kept bumblebees with these species and they got along handsomely (have experience with all but the rams- want to try them eventually, though.