You certainly can, although you'll probably want to add or upgrade a few things. I would suggest doing some reading before tackling a SW
tank, as FW
are pretty different in some respects. In such a small tank, staying on top of water parameters is crucially important, but it is doable. Also keep in mind that you will be limited to most likely 1 fish, although there are a number of cool inverts that you could have also. With the stock tank lighting you won't be able to keep any corals but a FOWLR
(fish only with live rock) tank would work well and is a good way to start. I had a 10g FOWLR
before I went to a 30g reef.