Your betta will be so much happier in that 10 gallon. The ottoes will be fine. It also really all depends on the betta because some of them are very aggressive and some are peaceful. I have put mine in community tanks always but my flagfish recently attacked mine. I have had my betta get attacked worse than the betta attacking anything else. I would also consider getting some cories too. They will somtimes flare at them but they never do anything. Cories are great fish. ;D