30x12x12 fish stocking

So I recently finished the cycle for this tank, and i was wondering if anyone had any suggestions as to fish stocking for this tank? i'm very open minded to what to keep.. i do not have any corals in there yet, so i am also thinking of maybe going live rock only and keeping non reef safe fish along with a few other shrimps and crabs that are also non reef safe, treat it as if you're keeping a new tank and give some stocking ideas! I don't want to keep fish that my other tank already consist of though however except for the cleaner shrimp maybe.

Other tank consists of:
yellow tang
singapore angel
2 occelaris clowns
1 lawnmore blenny
1 yellow watchman goby
1 twinspot goby
1 green clown goby
1 pistol shrimp

2 cleaner shrimps
5 hermit crabs
10 turbo snails
1 starfish
1 pencil urchin

Also, if i wanted to get a blue hippo tang to go with the yellow tang in a 55 gallon, would i run into any problems you think?

 

Hmmmmm. 19g tank. I would put a clown trigger in there. I am not sure of it's maximum size, but most triggers get to about 6" if I am not mistaken.

Now, the blue hippo idea. I wouldn't. Your 55 is already potentially overstocked IMO and the hippo will get to 12". It is of the large variety. Your yellow will get to about 8" and outgrow the tank. Your total inches exceeds 20 once they all grow up. And IMO, the tangs should be kept to a tank that is no less than 75g. And that is pushing it. Unless you want to get one small, let it grow a bit and trade it in. That is a possibility. But I still would not get another fish for your tank.

 

Wow, I read that wrong. I thought that triggers pretty much maxed out at 6, maybe 7 inches. No experience with them here. Obviously. Oops.

 

tangs don't go with each other, unless there are atleast 6 even then its a gamble. tangs may tolerate each other if the body shape and color is sufficently different, even then it can turn deadly. tangs see each other as a threat to their food supply. in such a small tank i wouldn't have more then one. there would be no place to hide for the weaker tang if things turned ugly

 

I think a 10g would be suitable for something like a Peacock Mantis. Lots of room for it to chase it's prey and move around. And I do believe this variety can get to about 6 inches.