Why are my goldfish fins turning yellow?

My goldfish is turning black?

• I bought 2 goldfish at christmas time so only 6 months ago, One has grown slightly larger than the other and its fins and tail have started to turn black on the ends and is slowly all turning black. any ideas? thanks

• Answer:

  Black can be natural colour changes, but can also indicate the onset of ammonia burns and fin rot. How are you keeping these fish? Goldfish are very large growing and very messy fish, any trace of ammonia in that tank caused by mess/waste food can trigger brown/black burns which also effects their insides and scorches their gill tissue so they suffocate. Test your water and make sure your tank is big enough - very very few people keep Goldfish correctly! For fancy Goldfish they ideally need a minimum of 20g for the first fish, 10g per fish thereafter. For long-bodied common Goldfish double that as they get larger and are much more active. Their tank also needs to be over filtered with weekly partial water changes and gravel vacs. They are pretty high maintenance fish!