Welcome to the hobby. To get this out of the way, you need to know that 20 gal tanks are a little harder to keep good readings. I had a tank that size for almost a year with very few problems but I had good filtration. I agree that I wouldn't get into corals until you were more familar with saltwater as they are far more delicate. With smaller tanks, you really need to keep up on the water changes and do regular tests for amonia, nitrite, nitrate to keep your fish healthy. For filtration, I used an empiror 280, about 40 lbs of liverock and very few fish, and of coarse a clean up crew. in case you don't know what a clean up crew is, it is crabs, snails, etc that scavenge to keep the tank clean. This is really important. Make sure you do not overfeed. Not only for the fish, but for water quality. Decaying food causes fluctiations in your water. There is a big debate on live sand or crush coral. You can do a search and make that decision for yourself. I personally like crushed coral (med). Fish for a 20 gal need to be smaller like, clownfish, 6line wrass, bangi cardinals, blenny's, goby's, and more. some people like damsels, some don't. I don't because they tend to be teritorial and tempermental. In a nutshell, agressive.
Hope i have helped.
Playtime
