The Knights are likely to eat your Bumblebees, but might be okay if you give them plenty of hiding places that the knights can't get into. The knights also like to hide in pipes.
I have a 109l (about 20g) at the mo with a pair of knights, a clay goby and 3 mollies. The mollies are big enough not to get eaten it seems!
Er....would suggest only a pair of knights cos they can be territorial and maybe 6 BBGs? Could always include some amano shrimp if you want more variety.
