You probably skipped a cycle because you used all live rock, but in the future dont try and cycle with a fish, just toss in a piece of uncooked shrimp it works just as well.
I would remove the maroon because they are mean little things, and then plan out your stocking list. If you do want a maroon, add them very last. Remember you are limited to one fish for every 10 gallons, so you are limited to 4, max of 5 fish in that.
There are lots of good fish out there for a tank that size, I would check out dwarf angel fish, blennies, gobies, clownfish, dartfish, etc.. Check out this site for ideas, there are literally hundreds of good fish out there, its all about what direction you want your tank to take.
Saltwater Fish: Marine Aquarium Fish for Saltwater Aquariums
Some other improvements I think you need to make for your tank are increasing the amount of rock, get rid of the canister filter and increase your flow.
You can buy dry rocks, which is much cheaper and will become live after being in your tank for a few weeks. I like
MarcoRocks Aquarium Products for buying dry rocks. You want 1-2 lbs per gallon.
Canister filters need to be cleaned pretty frequently to prevent water quality issues, which isnt such a big deal in a FOWLR tank, but can still lead to algae problems. You really can just do regular water changes and be just fine, or invest in a protein skimmer.
Having enough flow is super important, you want the volume of your tank turned over about 30x per hour. This will keep your tank well oxygenated, otherwise you can actually suffocate your fish.
I think a dwarf would be ok in 37, they dont move around too much, but they can eat fish that are about the same size as they are so they really limit what you can keep with them.
