Fin Nipping - But Who Is Doing It?

[xxBarneyxx]

Currently we have:

9 Blue-green reef chromis
1 algae blenny
1 Coral Beauty
1 Green coral goby
1 purple firefish
2 perc clowns
1 spotted mandarin
1 royal gramma
2 anthias (1 male, 1 female)

The bigger perc, mandarin and the male anthias have all had chunks taken out of their fins recently. The mandy and anthias where out of the top of their tail fin and the perc was the bottom of its anal fin.

The problem is I have no idea what has done it. While I have been watching them I have seem very little aggression at all. The royal gramma has always had it in for the perc but has never bothered with any other fish.

I'm guessing it could be the coral beauty (seems the most likely suspect) but I have never seen her attack anyone.

Just wanted to get peoples ideas on what they think it could be?

 

[AK77]

Are they true percs? If so, my money would be on one or even both of them. Mine were b#####ds for it. I had 2 of them and 2 false in my 180L tank a couple of years back. They tolerated one false perc but when the other was added, they would beat the granny out of him. Apparently 3 was company, 4 was a crowd lol.

They also got a bit territorial and would often hound the bangaii cardinal and the chromis. I had a coral beauty and never saw any aggression from it.

 

[xxBarneyxx]

I think they are true percs but have never been able to properly count the dorsal spines. The larger one is aggressive if anything comes near its torch coral but I have never seen it actually bite anyone (it just swims at them). The smaller one is tiny (probably the smallest fish in the tank) and seems to get on fine with everyone (he actually tends to swim with the chromis most the time).

It could be though, we are watching them all closely and will probably never know until we catch them in the act.

 

[Buddyboy67]

Is it happening at night or any chance of a pic of one of the bites??..beautys can be little nippers when established..could be a rogue crab doing it at night time though thiss would appear more frayed than a bite shaped damage...
What size are the chromis??..these peaceful little shoalers can turn into little psychopaths when paired up and in breeding condition, making even the worst damsel look like a little pussy cat

I know my percs, both pair, are nutters but most damage caused by them is more in the form of split or torn fins