Firefish aggression in a nano frag tank

TroutWithLegs · Mar 11, 2020

Hey all, wanted to see what advice and experiences y'all have had with fish being aggressive in smaller tanks, and how to deal with it. I recently added a pair of firefish to my frag reef and their behavior has changed drastically from the fish store, to QT, to now. I was under the assumption they were a mated pair, or at least a male/female pairing, I'd observed the two in a pair at my lfs in a tank with a dozen or so firefish, and have been sleeping together the past month while under quarantine, without any serious aggression. Now 3 days after the move to the DT are displaying some serious aggression, with one really tearing into the others fins.

I don't think they're hermaphroditic fish, and am wondering if having an environment with more fish could have triggered the change in behavior. Anyone have any advice or experience reducing this kind of aggression or thoughts on what could have triggered the change?

Big G · Mar 11, 2020

Even in my 90, one of my Firefish kept after the other one in the tank. And yes the aggression increased with time.

NJDragonet · Mar 11, 2020

Well that sadly can happen with any fish firefish can be very aggressive to each other. WATCH OUT I NOTICED YOUR TANK DOES NOT HAVE A LID FIREFISH ARE ONE OF THE FISH THAT JUMP THE MOST THEY WILL 100% JUMP WHEN THEY ARE BEING BULLIED. Also move the injured one to QT so you can re asess

TroutWithLegs · Mar 11, 2020

I was worried about that Big G. wondering if its something that will increase over time.

And thanks for noticing NJCoral, I do have a screen lid for the tank, I just took it off to feed and take some pictures.

Big G · Mar 11, 2020

TroutWithLegs said:
I was worried about that Big G. wondering if its something that will increase over time.

And thanks for noticing NJCoral, I do have a screen lid for the tank, I just took it off to feed and take some pictures.

What's really weird is they hung around together in QT, and then again in the 90 for months. Then all of a sudden, one was hiding in a corner.

lebreef · Mar 12, 2020

i had a the same thing happen to me with a "pair" of Helfrichi Firefish. They even slept in the same PVC tube in QT and in the same whole in DT. I was happy that I had a pair! Again, one day noticed one with some teared fins, looked for the other and lo and behold it was attacking aggressively. Now each of them has taken a side of the tank but there is a clear dominant one. They seem to tolerate one another for now and aggression has subsided a bit but I have a feeling that will not last.

NJDragonet · Mar 12, 2020

Big G said:
What's really weird is they hung around together in QT, and then again in the 90 for months. Then all of a sudden, one was hiding in a corner.

I agree I did some research if there where more firefish in the tank at the lfs he may have picked up 2 males or 2 females firefish can be big schooling fish maybe after a while the males no longer got along the agression is more one on one if you want to keep them I would reccommend adding another firefish as soon as possible so the agression is more spread out and a higher archy will be formed. If you do not want to keep them remove one of them if it is the bully move the injured one back to qt so he can rest a bit. If you want to remove the injured one then leave the bully in the tank

TroutWithLegs · Mar 12, 2020

I've decided to separate them for now. I put one of the QT tanks back together, and put the bully in there. While i was waiting on the water to come up to temp, i put the bully fish into one of those little acclimation boxes in the DT, and immediately the other one came out, ate and seemed to behave less stressed. I'm going to keep them apart for a week or so, and see if the damaged fins improve, and if any local reefers want to trade the bully for anything. If not, im gonna put together another nano tank just for him....