Thank you for your inquiry. I would first need to know if you are looking at setting up a reef tank or a fish only system. From there we can plan out the best course of action for you. I would recommend either calling us directly (1-800-566-FISH) or emailing us email@example.com as it will be easier to discuss back and forth with you what to do. I have also linked a couple of articles below that I think might help some:
Restoring a neglected tank parts 1 and 2:
If there is anything else we can do for you please let us know.
Marine Depot Customer Service