Atlantic Blue Tang brown spots

[Hanekochan]

Hi, I'm new in this hobby and i've had my juvenile atlantinc blue tang for 2 months more or less. Yesterday I did my big water change (70% change) so I went to bed hoping my corals will be bigger today haha... But unfortunately my tang woke up like this, and even whiter than normal (when it's really healthy its color is already more blue than yellow)

I've notice that (apparently) it tend to hit itself a lot because I've seem it with some white patches before that tend to heal by themselves. I don't know if my tang was crazy last night and now it's really wounded or if I should worry now.

I haven't have the time to check parameters today, but before the water change I was worried only for the nitrates that went from 25 to 50 ppm. So last week I installed an algae refugium and yesterday change the water (70%).

Thanks!

(The brown spots are on both sides)

 

[Jay Hemdal]

Welcome to Reef2Reef!

Given the recent large water change, I would say these are injuries. When the water level drops low, the fish can panic and thrash about. If the lesions don’t get seriously infected, they will heal on their own. Going forward, a couple of smaller water changes would be less stressful to this fish.
Jay

 

[Hanekochan]

sadly, it died last night :'( ... I'm so sad, I don't know what happened...

 

[Lost in the Sauce]

Very sorry to hear that. What was the purpose of such a large wc?

 

[Jay Hemdal]

sadly, it died last night :'( ... I'm so sad, I don't know what happened...

Sorry to hear. If those were marks from an injury, they didn’t appear life threatening. How do the invertebrates and other fish look?
Jay