Kessil

Aggressive new fish

So I introduced a pygmy cherubfish to the tank (daughter named it "Topaz"). It's being fairly aggressive towards the clownfish ("Wiggle-butt"). The Clown has a nice little "den" area in the front corner, hosting a couple Duncan mushrooms. The Cherubfish has taken to swimming over during feeding time and just hanging next to the clown; the two of them have been doing the charging at each other, waving their rear fins at each (enough to cause sand to swirl). No nipping as far as I can see.

Should I try to isolate the Cherub for a bit? Intervene when they "fight"? Not worry about it?

I've been trying to target feed in the area away from the Clown first so that the Cherub has less reason to head over to Wiggle-butt's territory to no avail.
 
I have a couple of pygmy cherub angels
in my 125, and they can be aggressive little punks (but I love them anyways). First, how big is your tank? Despite being small fish, they really do need a decent amount of room. I had mine in a 70g before, and I can’t imagine them being sane in anything less that a 3’ tank. They will probably always be a little belligerent, but your situation sounds more like posturing right now. In my experience with overly aggressive fish, if it was the last one added, removing it and reintroducing later probably won’t help much. As long as your clown is eating and hasn’t been chased to a top corner of the tank, I’d give them time to get used to each other, and see if they can settle in together.
 
It's a 24 gallon, so a bit small. The last Cherub we had was very gentle and not aggressive at all. Might have been an anomaly.
 
Yeah, IMO, that’s a bit small for a Pygmy angel to do well longterm. But I’m not the fish police, and you’ll be able to tell when/if the space no longer works for it. I’ve had 3 of these guys, the 2 I have now, and one I mysteriously lost probably 2 years ago. They were all bold, confident and pretty obnoxious.
 
Cherubs are one of the smallest angels with the flame back, fishers, and white tail. I kept both cherub and white tail fine in a 34g cube but I got them real small, like quarter size, and they grew to ~2".

He and the clown will probably chill after a bit. I recall some chasing early on too.
 
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Terrible quick big of my larger cherub. Tough to measure, but I’d give him around 4” and I’ve had him for around 4 years or so. As a point of reference, that yellow tang has been in captivity for at least 5 years.
 
I had a cherub in my 5’ display that decided he didn’t want to share his tank with my clownfish and attacked them mercilessly until I rehomed the cherub. I think clownfish get targeted because they stay put and try to defend a small territory while other fish will learn to stay out of the cherub’s way.
 
Alright so update....I moved the Clown's nest (an aquarium decoration hollow globe with openings and a couple Duncans attached) from the right side to the left side because the Cherubfish was hanging out in a little cave on the right hand side near the Clown's nest. Guess who decided to also move and is now hanging out inside the hollow globe. I don't know if the Cherub hates or loves (in a stalker-ery way) the Clown. I might need to rehome the Cherub. (Or get a bigger tank....but that wasn't in the immediate plans). I'll give it a few days to see if things settle down (Cherub does a great job on hair algae and hydroids).
 
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