5 gallon decision

I have a 5 gallon fish tank. Salt of course and it needs stuff to be put in. It is cycled and has been tuning for 2 months now. I have a crab and a Bangaii cardinal fish. I know that it was a mistake. I talked to someone at my LPS and said it was fine but then told no when I went online to d reading. I will find a better home for him somehow but my real question is, what should I do to give this tank life? My original plan was dwarf seahorses buy after reading 2 months of research, I think that the feeding will become no good. I need a tank with life and happy fish and hopefully coral.





Open to anything. As long as the fish r happy and the tank will be safe. And I have to go the same LPS because it's the only one in town. So I will take my thoughts from here and buy what people think r good with this 5 g.