Ive added a diamond goby to a 50 g tank with 2 small yellow fin damsels, and a purple dottyback. Was told and read theyd be simpatico. Appears not. Goby is scared. Will this get better? What if I add an equalizer - something larger than the purple?
They usually have strong personalities and it should with time become less timid. I had a tank in a low traffic area in the basement and it would hide when I walked up to look. Once I moved it to a more central location they are got used to seeing people.
Also does one of the other fish chase it into hiding? If it does a larger fish will do nothing. It's the pecking order honestly I hate damsels they are highly territorial and will stress a new fish to death. Get rid of the damsels would be my suggestion. 50 gallons is small for territorial fish.