Did you 'seed' your tank from someone else's? I mean take a few chunks of LR
and scoops of his/her substrate? If you did, you may be ok to add corals in a month or two.
What about your live rock? Did you get it uncured in the mail or from the LFS
? That can make a big difference in how long it takes to cycle and/or mature your tank. Even if you buy 'pre-cured' LR
mailorder, you must cure it again due to dieback in the shipping process.
If you stated from scratch, brand new substrate, almost sterile rock, I would wait at LEAST 6 months before you try and add coral as your water parameters will bounce all over the place when the fish are added to a system that small.
Once your fish are in there, and if you are testing every couple of days, if everything is stable after a couple of months, you should be able to start off with some corals. I would recomend trying them out in this order:
Here is a BASIC list of corals for you to try:
Mushrooms - low to med light, very easy to keep, will spread over time
Zoos - med light, very easy to keep, but they will spread like weeds.
leather corals - med to high light, not to hard to keep
- torch, frogspawn, brain, etc - high light, try these much later, water must be great.
I would try frogspawn or bubble, they seem to be more forgiving.
- acropora, scroll, etc - very high light, try these last, water must be perfect, all the time. Good luck - I have only been able to keep a scroll coral frag growing in the top 1" of my tank
I would stay CLEAR of ANY coral that is "no light requirements" These need to be fed each and every day, since they are non-photosynthetic. You can easily foul your water in a tank that small by over doing it.
These are most gorgonians, sun polyps, chili coral, carnation corals and the like.
Hope this helps