I threw one together for a quick isolation tank when a captive raised matted file fish was too small for my main display. It was the size of a dime and couldn't handle the tanks flow. Ended up in the over flow for a bit then sump. Had one of these sitting around so took some of the tanks sand, a rock or two, and next water change used left over water. Everything fine and it worked well.
One of the rocks had some green button pally / polyps and the stock light didn't do much for it. So I had a old DIY royal blue, cool white LED that I made. Removed some of the lights so not to over power it and placed it on the glass lid. Worked very well. Put in a few coral frags that I made - all soft - and it did better. Xenia and Fuzzy Lobo. Anyway once the fish grew after 2 months I moved it back to the display and moved everything with it.
You are looking at a Nano tank. So zoa's, mushrooms, some LPS and SPS will work but a lot depends on the lighting. I was going to build a stand out of 2 x 4's and a 1/4 inch back board to hang a low intensity LED light. You don't have a lot of room although it is deep. You want to try and prevent burn or too much intensity yet keep spectrum control.
Long and short of it is:
Small fish - clown gobies, pistol shrimp goby pair, fire fish
Corals - depending on light - zoas, soft, lps, and sps can work.