i have a 20 gallon reef tank and i was wondering if my lighting is good. it is that Current USA
Nova Extreme High Output T5 Lighting Fixtures and i gives out 96 watts so a little more than 4w per gallon. if this is ok can you tell me some cool coral that i can keep. i am going to keep two clown and one fire fish and some snails and hermit crabs and also a star fish

4watts or so per gallon is very good for a reef tank.
You could get away with all soft corals and a few easy hard corals!

I would suggest easy stuff to begin with, mushrooms, zoanthids - star poylps, button polyps, clove polyps. You could also get something like a toadstool coral or cauliflower coral, they look amazing!
And soft corals will do!

As for hard corals I would suggest starting with something easy, such as a brain coral, make sure you place it near the top of the tank for it to get the mose exposure for photosynthesis!

That lighting is fine for most corals, just nothing that needs "high lighting" but it will accommodate "moderate/high" light needs. pets question and answers,www.5d2d.com

Almost all softs and LPS are suitable and several SPS like horn corals and montipora. Put corals that have higher lighting needs at the top of the tank, and corals with low lighting needs at the middle to bottom portions of the tank.

Watch out on starfish, not all are reef safe, and those that are reef safe often do poorly in a 20 gallon tank as they need a large area of live rock to feed.

What is your setup? Are you running a skimmer? What total flow rate do you have in the tank? That will help narrow down your coral selection. Good beginner corals that can be bright but easy are zoanthids and mushrooms, toadstool and cabbage leathers, etc. With hermit crabs, best to avoid most LPS, especially elegance corals that often suffer from the crab walking across them.