Well I know a guy who has a 38gal tank and has 4,000gph flow. If you keep SPS you may want to immitate him (100x flow). Have you figured out what kind of corals you want to keep? Either way you will want much more than what you have now. I would suggest looking into a closed loop system. You will need a large pump, maybe something like a quiet one 6000 or 9000, some plumbing and either, bulkheads and nozzles, or spraybars.