Starter coral? Some more fish/invertebrates? Suggestions?

[Ben10]

Starter coral? Some more fish/invertebrates? Suggestions?
I have a 20g tank, protein skimmer, live rock etc. and I have a pajama cardinal, an ocellaris clownfish,1 coral banded shrimp, three turbo snails, and a green mushroom coral.
Also the lighting is a 17 watt, T8 coral sun bulb.
I've had the tank for 6 months now.

 

[slitherbomb]

Check liveaquaria.com they have a section called starter coral lol

 

[iDream]

I doubt you'd be able to support corals with that bulb.

 

[Ben10]

What bulb would you suggest?