I would not personally suggest fish in a 3 gal, I figure I only have 2+ gallons of water in there. LR ,sand ,heaters, take up room . I have one fire shrimp that I just love, shy at first, now up on the front begging for food all afternoon. I hand feed him with a pippette along with my crab. I also have some snails in there, started w 2, now have 4 babies too.
The tank came with the 13 watt PC bulb, that is working out nicely, I have awesome bright green algae growth on the LR, and all is going great. I added a blue LED above the tank ( mounted under the cabinets above) that makes for a great looking reef at night.The corals flouresse at night, totally awesome to watch.
You will need a big heater in that tank, it looses heat, I bought this one.
Aquarium Heaters: Visi-Therm Deluxe Heaters
I tried 2 10's and it would not keep it warm, so I had to go w a 50, no problems with this one, I still have one of the 10's in there for back-up.
I also had a glass company build me a 1/2 top for mine, to prevent stuff from getting in while working around it in the kitchen, cost me $10. Here is a picture of it on the tank.
If you need a better pic of top, just let me know. I took cardboard and traced around the tank, giving an extra 1/2 inch , I also left the back 5 or so inches open, and I stuck little tabs around the edges to keep it from sliding around.