Unknown aggression... ???

Looking in my tank this morning, my firefish was swimming at a bottom corner, well away from his "sleeping" spot. At closer look, the back half of his dorsal fin had a few bites taken out of it. I've never had an issue with aggression in my tank before, all inhabitants usually swim in the open together.

Question is: who is the culprit, and what could cause this? Anything I can do for the firefish, or let him be?

Stocking list: 1 hippo tang, 1 yellow tang, 3 dispar anthias, 2 blue chromis, 1 sixline wrasse, 1 firefish, 1 true perc clownfish, 1 yellow watchman goby, 1 skunk cleaner shrimp.

The firefish sleeps close to where the hippo, sixline, and yellow watchman sleep. I feed either ~2/3 cube food a day, or 1/8 cube and a 2x3 sheet of nori a day (usually alternating), plus a ml or two of plankton in the morning for the anthias.

Thanks for your help!

 

IMO, several of the fish you listed are potential candidates for being mean to a firefish.

Additionally, you are rather heavily stocked and this lack of space will encourage aggression.

 

IMHO - it's either the hippo or the fact that there are two larger tangs which are not really well suited for that sized tank which are inducing extra stress and therefor territorial aggression. It's not the # of fish you have but the two tangs in a 90 gallon tank that may be contributing to your tank's aggression. Also clowns are damsels and therefor can be quite aggressive. Again, lower stocking rate/level might help to alleviate this problem.

 

Thanks guys. I am aware that I'm overstocked, and while I WILL NOT be adding any more fish, I have been contemplating removing the chromis and maybe firefish to lighten the bioload. Hate doing it though, they're all like family.

Water quality is not an issue though, I'm at 0 nitrate 0 phosphate. Just room... time to get a bigger tank!;D

I also have switched to a lighter feeding schedule (as described in OP). I used to feed heavier, but came under the impression I was overfeeding... perhaps not?

 

My guess is the sixline. My flasher wrasse picks on my firefish and leaves their fins quite tattered.

 

This is my guess too. Yesterday I saw the sixline dart at the firefish, but no contact was made... I've read that sixlines and firefish dont neccessarily get along...

 

Fire fish are one of my favorite fish, but IMO they are too passive and shy to be in a tank with larger more aggressive fish and active fish. The list you included has a lot of potential suspects. They can injure themselves just from trying to get to their bolt hole to hide. Since they sleep in the bolt hole it also makes them vulnerable to inverts like crabs and brittle stars.

I hope it works out, they are really a lovely little fish.

 

Thanks Cheryl. He's one of the original fish that came with the tank, and pretty good size (3"). The injury is definitely from nipping.

I do have a QT tank if things get worse, but I hate to stress the little guy more by chasing him around the tank. He's fast...

 

If you do have to capture him, the best way to do so is to find out which bolt hole he prefers and remove that one rock. I have captured a number of them this way.

They can get much larger than I once thought. When I was at the Monterrey Aquarium last summer they had some that were 5 inches. I asked a staff member and he said they were between 3-5 years in age.