Black marks on Moorish Idol and Powder blue tang

[Lefeta]

Hey everyone, just wanted to know whether anyone has experienced this before, and if its normal? I’m just concerned because my powder blue had similar black marks 2-3 weeks before dying of an unknown cause (which would eventually end up killing half my fish: tangs and angels). I ended up treating it with Formalin, and since then i’ve had no other casualties (I also have a royal dottyback, midas blenny, and 2 clowns). I’ve had the Moorish Idol for almost a week now. His been eating well and has showed no signs of weakness or irregularities. In the past couple of days his developed this same mysterious mark.
Tank:
- 350L
- Salinity: 1.025
- Temperature: 25 Degrees celsius
- Ammonia = 0 (don’t have exact value)
- Nitrates = 8ppm
- Calcium = 400ppm

 

[Doctorgori]

Off topic but that idol looks a lil thin in the forehead, is she eating well?

 

[Lefeta]

Off topic but that idol looks a lil thin in the forehead, is she eating well?

I got her last sunday. She only started eating 2 days ago, hence why she was skinny. She’s eating well now though. Thanks for checking up

 

[Lasse]

Normally - black markings in fish are often signs of healed mechanical damage. The fish transport up melamine to the wound (an antiradical) as a sort of defence mechanism. Hence - the black marking. I do not say that this is the case in this actual case but have that in mind when you decide what to do. That the fish have start eating and eating good - is a very good sign - so do not overreact.

Sincerely Lasse

 

[Lefeta]

Normally - black markings in fish are often signs of healed mechanical damage. The fish transport up melamine to the wound (an antiradical) as a sort of defence mechanism. Hence - the black marking. I do not say that this is the case in this actual case but have that in mind when you decide what to do. That the fish have start eating and eating good - is a very good sign - so do not overreact.

Sincerely Lasse

That’s wonderful news. I guess i’m just a little worried about last time. I’ll probably hold off on dosing the Formalin then. Thanks for the insightful information!

 

[Lasse]

That’s wonderful news. I guess i’m just a little worried about last time. I’ll probably hold off on dosing the Formalin then. Thanks for the insightful information!

Yes but observe the fish very well - I´m can be wrong and you maybe need treatment but IME - black markings is often old wounds. It is difficult to judge with just a photo

Sincerely Lasse