you'll be happy with a 30g (29g). They are great, I'm possibly upgrading from it soon though, i got a good deal on a 55g corner ($100) but I have nowhere to put it and im moving from indy to florida/ georgia (college) in like a year, so I dont know how smart it is to set up a larger tank just to take it down in a year.
the turnover rate is good, maybe a small powerhead would make it nicer, but you should be good.