Clarkii fin trouble

[Hamerhed]

I asked this question twice in the desease forum and didn't get an answer so .....

The smaller of my 2 clarkii's which I've had for about 4 months developed what looks like black discoloration on his fins almost immediately after I got him. I had decided it was caused by him hosting in my hairy mushroom. Today I noticed that he's missing some webbing on his dorsal fin. He never slowed down, has always eaten well and only today seems more shy than usual. The other Clarkii is unaffected. You can see both the discoloration and the dorsal fin thing in the photo. Any help will be appreciated...

 

[MarinaP]

Could be two unrelated events. Darkening looks fine.

Dorsal fin is physical damage. I would look for a night predator, such as a crab hitchhiker.

Or the female is beating him up.

 

[Hamerhed]

Thanks Marina. The dorsal fin was fine 2 days later so I guess someone did try to take a bite out of the little guy. Life is tough on the reef...

Do you have any idea what is causing the darkening of his fins. The only coral that was in the tank when it started was a green hairy mushroom. But to this day I have never seen him go near it.

 

[WDLV]

I really don't think fin rot when I look at that pic. It looks like either natural darkening or like something is irritating it. No other corals, bad water params, abrasive hosting site etc???

...and I agree with Marina that the dorsal looks like injury which could very well be the cause of the darkening too.