I would be cautious about using a tank that small for a reef. The more water you have, the more room you have for error and the easier it will be to catch a problem early and fix it.
I don't want to scare you off because this is truly a great hobby and you will be able to enjoy the results on a daily basis...... but everything about saltwater is expensive, and the tank is just a very small part of the start up and maintainence cost.
My advice would be to start with at least a 55 gallon tank, a good skimmer, a lot of live rock and use your free 30 gallon tank to create a sump underneath for your main filter system.
If you spend on the correct setup, you will save yourself a lot of aggrivation
