Hi, I have a 3" sailfin tang in my tank and today a friend of mine offered to give me some free fish including a Sailfin that was identical to mine only 4"-5". I checked my marine atlas which said only keep 1 unless it's in a large system. I have a 500 gallon with 350lbs of rock and about 20 fish. Well, the original sailfin just went crazy and he has been chasing the new one around like crazy and keeps pecking at him. It looks like he would rather have him dead. Anyone else have this experience and do you think they will calm down after a few days like alot of tangs? Thanks in advance!