knight goby

So because I am now restocking my 38gal brackish tank, I decided this time to ask you guys about fish compatibility so I don't make anymore mistakes. I currently have two black mollies and three knight gobies in the tank. But I plan to restock so that my stock will be six black mollies and ten...

Is it possible to keep knight gobies in groups or pairs, or must they live alone? Asking because I read on one source that they are aggressive with each other, but no other sources seem to agree. Thank you!