I have a 7 inch SAL in a 10 gal right now... I got him at 1.5 inches and had him in a 2.5 gal, once he reaches 10 inches he is going in a 55, then eventually my 125. I have the best luck feeding my SAL black and blood worms, I also give him pices of shrimp, cucumber and the occasional guppie whom he has no problem catching as long as there is vegitation on the top. My LFS has about 15, 5 inchers in a 20 gallon with no deaths... There a pretty peaceful species for being a lungfish. Especially as babies... As long as they can't easily fit in eachothers mouths, so aslong as they are all about the same size I would say you should have no problem.