They're in a 7 gallon tank, with a betta whose nose is a little out of joint but who's adapting pretty well to his new buddies. I was originally planning on only adding 2 otos, but figured with their low survival rate I'd toss in an extra. So far all 3 seem happy and healthy.
The tank had enough algae that they're keeping busy, and if they were starved, they should have a decent chance at recovery. Right now they seem to think it's buffet time.
My wife wants me to set up a second tank. If I do, I'm thinking of a 16 gallon. One or two of the otos could eventually end up in that one. For the moment, I need to watch the numbers on my water and make sure the tank can handle the 4 fish.