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I would highly recommend that you either make the tank a freshwater tank or start with a larger tank. To give you an idea, I just started a 4 gallon tank (build thread under name) and I am 500 dollars into it. Guess how much livestock I have? None. Also realize that getting any more than one fish in a tank this size is a bad idea. Some would argue that getting a fish at all for a tank this size is a bad idea.
It may seem as though a smaller tank should be easier, but this is simply not true. If you are interested, check out my thread and have a look through it to get an idea. Then check out a few more threads. Then check out a book on saltwater tanks. Formulate specific questions and then post them here. Tanks of this size are usually left to those who have experience in the hobby.
There are tons of helpful people here and we hope you stay because we have a lot of fun and we would really like to help you.