Please help with fish addition

I am at a standstill with my reef tank. I presently have a yellow tang, bicolor angel, 2 ocellaris clownfish and a yellow watchman goby. Wanted to add a firefish and 3 blue green chromis but one of the chromis harassed all the others to death while in quarantine. I am returning the surviving chromis to the LFS but every time I look at a fish that i like i find that something is holding me back. Loved the wrasses but found out they would eat all my crabs CUC. I like fish that are active swimmers. I like the firefish but I am afraid that being a peaceful fish my yellow tang and bicolor would harass him. Don't know if fire fish will get along with my yellow watchman goby.
Can anyone, with my present fish stock (they all are getting along great) make a suggesting that will not result in bloodshed?
I am so frustrated I though of leaving well enough alone but the 75 gallon tank looks pretty under stocked.