Goldfish red blotches

[GanaM]

Hey
I just noticed some darkish patches on my goldfish. In a stable 160 litre tank. Ammonia 0 Nitrite 0. Regular weekly water changes. Is it just pigmentation or disease? The fish is active, responsive, feeding etc..pics attached

So grateful for your opinions!
Gana

 

[SaraB]

Red is usually caused by ammonia or nitrites being too high. However if those are both 0 and he's acting normal then it may just be him changing his colours on you.
What are your nitrates?

 

[GanaM]

Nitrate

Hi
Thanks for your reply! Nitrates are 5.0.