ok i have a few words of advice for you bud,
1.) get that damsel out while you can or anything you put in the tank after that little guy will feel his wraith.. no joke.. since he was the first added he has claimed all of your tanks domain i promise you.
2.) a uv
sterilizer has no place in the reef keeping hobby, its mostly a freshwater thing to treat algae and other bacteria like ich, but in the reef keeping hobby algae and bacteria is what you need for your tank to thrive, so in turn it does more bad than good.
3.) your best bet for a 27g hex is probably going to be a single taotronics or comparable 120w dimmable led
fixture thats actually reef capable.. link--> 120W LED Aquarium Lighting Full Spectrum Coral Reef Growing Moonlight Dimmable | eBay
4.) i didnt read anything about a filter system in your post so im assuming you dont have a sump, and if your going to want corals your going to need a skimmer a small one would work but since you have a hex tank your very limited in choice, like an aquaticlife 115 or a hydor slim skim theyre both in-tank skimmers and worked great for me and your corals will love you for it.