It will depend on the fish it self. Sadly I happen to have a beautiful yet very nasty Mystery wrasse. I got it at tiny size, and it did not help. When he went in my 155 there were 10 or so wrasse. Little by little all but 2 of the original wrasse disappeared leaving only the possum, and the 4 line. I've tried replacing the missing ones on numerous occasions, and they all disappear. I'm I 100% sure it is the Mystery wrasse's doing no, but before it all the other wrasse were fine, including the yellow coris which was in my tank for years before the Mystery.