Parotfish becoming white

[helptoall]

Hi. Her color started to change yesterday and becoming more and more pale, today shes like this.. She is active and has appetite. She is in a 450L tank with 3 small iridiscent sharks, 3500L/H filteration ,weekly 30% wc. Parameters are 0,0,10. wter temp is 28. she has her corner with a jar gravel and decorations.
Any ideas? thank you

 

[Colin_T]

What's the pH and GH of the tank water?

Does the tank have substrate?
The picture shows a bare bottom tank, which is not good for fish. They need a layer of sand or gravel over the base. It doesn't have to be a thick layer, but they need something.

Have you added anything to the tank in the last 2 weeks?
What (if anything) did you do to the tank yesterday and the day before?

Are there any floating plants in the tank?
If not, get some Water Sprite or some other floating plant for the tank.

As long as the fish is still eating well and doing normal poop, and it is acting normally, I wouldn't worry too much.