Goldfish turning pink

[Squigglyo]

Hey guys

One of my son's goldfish is turning pink and im guessing thats not a good thing.

- It is a 60 litre tank (will move to a larger one if/when the fish grow big enough).
- Once a week I swap out 25% or so of the water (stirring up the rocks and sucking up whatever comes out).
- Each clean, ive put in Water Ager.
- There are 3 goldfish, only one has pink tail
- There are two sucker fish. one of them has started taking an interest in the pink tail
- There used to be 2 shrimps but they died and I did a full tank water swap (months ago now).
- There is a water filter that drops water in from the top
- There is a light that I turn on during the day and off at night
- The tank used to be near a window (which caused heaps of algea), it is now not near a window and has no more algea issues
- I feed them a large pinch of flakes maybe twice or three times a day

 

[Fishishy]

Your fish could be changing colour from a lack of light, as well as a lack of oxygen. I would be interested to know your water parameters because goldfish changing colours is not necessarily bad, goldfish have been known to change colours multiple times throughout their life, even when kept in perfectly optimal conditions. Your goldfish’s diet could also be a factor. To answer this question further I would love to know your water parameters and the brand of flake food.