Blue an yellow damsel

[Miss cruz]

Hi i have a little damsel called burt hes so cute i need a friend for him though an im so unsure on what to get i have a 55 litre saltwater aquarium atm its just him a turbo snail called kevin ha ha sonic our blue legged hermit an kermie an hermie our red legged any suggestions as i no i cant get another damsel thank youu

 

[Angelo russo]

Not sure what liters equals to gallons but I have 2 domino damsels and two bluefin damsels in a 40 gallon long and they get along fine I have plenty of rock for them and they have there own territory In tank but I have not noticed any aggression with them and I have them for 4 mnths no nipped tails or dominant ones the colors are beautiful