How Much?

So i have had my tank up and running for a couple months now, and i was just wondering before i go and buy something how much fish could fit in my 30g tank, I have 2, about 1 inch, dominos, and about and about a 1 1/2 inch blue devil.
So i guess what im asking is, how many more fish, how big can they be, and what should i get?

 

Starting off 1" of adult length to 4 gallons of water is the way to go. Right now you are at that limit. You have 15" of adult length with the damsels. If this is FOWLR you could add 1 or 2 more fish if you have plenty of hiding places. Damsels are more territorial as they reach adult size.

 

Depending on how many hiding places you have, I'd say you're stocked too. Damsels are very aggressive, so 3 in a 30 is gonna be full to them!

 

i do plan on making it a FOWLR tank, but when ever i talk to guy at my LFS he always tells me that the fish will only get as big as the tank allows so i didnt think they would get that much bigger and i did the fish calculator on this website and it said i could have about 8 inches of fish. and right now im lookin at about 3 - 3 1/2 inches right now. So i thaught i might be able to get about 4 more inches right?