Someone is Beating Up My Mandarin

[Dog Whiskey]

I have a captive bred (Biota) mandarin who has grown up in my tank. It's just over a year old and aside from one minor incident has been thriving. However, something over the last few days has been beating up its left pelvic fin with some minor damage to the right fin. It's eating and still swimming around, and has been lately palling around with a blackcap basslet.

There is nothing new in the tank other than an anemone, and aside from the basslet, none of the other fish pay any attention to the mandarin. I have an assortment of hermits, including three with large claws on one side and have noticed them getting feisty with one another.

I know the mandarin sleeps in the sand and does the whole camouflage thing at night. I haven't seen anyone attack the fish. Is it possible that the hermits are being jerks? I'm happy to remove them if need be.

Thanks!

 

[Pickle_soup]

What fish do you have? And most crabs are opportunistic omnivores. I do not trust them for anything.

 

[Dog Whiskey]

Aside from the basslet I have a bunch of other captive bred fish: two clowns, a coral beauty angel, a starry goby, and a pavo damsel. Plus a killifish that hitchhiked on some algae as an egg and hatched in the tank. The only issue is between the damsel and killifish, who terrorized the damsel when it was younger.

The only fins nipped on the mandarin are the pelvic fins, which is leading me to think it's something on the ground. I'm trying to catch the suspect crabs (the ones who have been fighting each other) but of course they're now MIA since I want to catch them. But i have a tank I can put them in to see if that solves the issue.

 

[kevgib67]

Anyway you could record the tank when you’re not around? Perhaps the culprit is shy or expecting to be fed when you are in front of the tank.

 

[Pickle_soup]

Aside from the basslet I have a bunch of other captive bred fish: two clowns, a coral beauty angel, a starry goby, and a pavo damsel. Plus a killifish that hitchhiked on some algae as an egg and hatched in the tank. The only issue is between the damsel and killifish, who terrorized the damsel when it was younger.

The only fins nipped on the mandarin are the pelvic fins, which is leading me to think it's something on the ground. I'm trying to catch the suspect crabs (the ones who have been fighting each other) but of course they're now MIA since I want to catch them. But i have a tank I can put them in to see if that solves the issue.

That's a really cool hitchhiker. I wouldn't be surprised if it was the Coral Beauty, mine is a little anus. Not terribly aggressive, but definitely annoys other fish. Picks on my juvenile Heniochus...he has no idea...

 

[Dog Whiskey]

That's a really cool hitchhiker. I wouldn't be surprised if it was the Coral Beauty, mine is a little anus. Not terribly aggressive, but definitely annoys other fish. Picks on my juvenile Heniochus...he has no idea...

I've heard they can be jerks, but mine is pretty chill. The killifish actually has been the tank terrorist, but now the damsel has put him in his place. And the basslet can be protective of his cave, but I've seen him and the mandarin literally swimming side by side and hanging out by the front of the cave together, which is hilarious given the size difference.

 

[Dog Whiskey]

Anyway you could record the tank when you’re not around? Perhaps the culprit is shy or expecting to be fed when you are in front of the tank.

Possibly, but I WFH and they're all pretty used to be being by the tank. This only happens at night, which got me thinking about the crabs. The weird thing is it's been zero aggression with no new crabs or fish for a bit now. Added an anemone about two weeks ago, but while others have been curious or swim near its perch, I haven't seen the mandarin by it at all.