Don't know why you bumped it, magikman nailed it. And make sure what you put in there is compatable as saltwater needs an ecosystem and to make it easier, make sure you pick of fish and sponges that keep a balance (though with the small tank your talking about, you really don't have to worry about this).
But like I said, magikman nailed it
[quote name='magikman']I did have a 55 gallon for about 5 years. With saltwater, bigger is better. It's a delicate balance of salinity, pH, and many other things. The bigger the tank (or tank+sump), the less of an impact a change will make. With an 8-15 gallon tank, you might get away with having one tiny fish, any more would probably die quickly. I could ramble for a while, but there are some great resources online. Checkout thereeftank.com.[/quote]