For a 29g i would get a school of about 15-25 exodons. Do a search on them if you need pics and info. But they are a great small monster. They have the attitude that piranha owners want out of there fish. Most of the time they have to be by them selves or they will kill most tank mates. And you have to keep alot of them in a confined space or they will kill each other. They are unlike most other fish in rules to be followed. You can check the other characins forum for alot of personal info as well from some keepers of these little monsters.