I agree that 6 clowns is too many to keep together in a smaller tank as they will fight, but if you have 6 small non-aggressive fish AND excellent filtration, you can do it.
3-4 small fish in a 55 is great, but there's no reason you can't have more, as long as you have enough filtration to remove whatever the fish put in. And, of course, prevent overcrowding. Some species need more room than others.
I also agree that you'll want a 55 or a 75 soon anyway, because I thought a 29 would be big enough for me. Well, it's not, but money's a big issue to a college student, so I can't upgrade it anytime soon. If you have the means to, though, I'd get a 75. It's just as long as a 55 so it really doesn't take up much room, and it's only a little bit wider. Plus you can have a fuge and/or a sump under/near it to give you even more water--the more, the better.
Good luck!!
