I originally bought 3 of these guys, 2 of them mysteriously disappeared but I've had one that has shown to be quite hardy, even survived an outbreak of some kind that killed most of my other fish. Can I add 2 new ones?

Also, can I add some trimma or eviota gobies at this point or will my green banded goby bully the new little kids on the block?

This is a 20g tank.

I currently house a GBG with 2 different species of trimmas, a red head goby, a highfin goby and a coral croucher goby in a BC 29. My red head and the GBG hang out together and I have never noticed aggression between any of them. I think these guys are the best fish for nanos. Go for it .

I have one GBG and one masked goby in a 5.5gal.