Thorne, Don't get a marine tank any smaller than a 29 gallon. Anything smaller and you'll have a hard time keeping your Ammonia, Nitrates, Nitrite levels stable unless you want to spend a small fortune in filtration. Also if you know anyone with a tank already established and they are willing to give you a few handfuls of rock/dolomite/sand and a little water from the tank that would greatly decrease your "break in" period. If you plan on using dolomite I can hook you up.