Why are your goldfish fins turning red?

Answer 1

The reason goldfish are any particular colour or intensity is all down to their breeding and genetics plus a certain amount of what the fish is/are fed (high carrotene content= high red colouration) and a bit of their apparent colour also depends on the kind of lighting the fish is/are under.

Answer 2

It sounds like it may have septicemia. You need to treat the tank / fish with a product that treats fungus. There are several available at your local pet store and even places like Walmart in the pet department.
Also, you need to do at least a 25% water change. It could be that there is bad bacteria in the water or poor water quality. Take a sample of it to Petsmart or your local pet store. They can determine if the water has too much Nitrite, Nitrate or Ammonia. High levels can be detrimental to the health of your fish and even cause it to die.
Some people think that you can just fill a tank with water, put a filter in it, add an air stone, feed fish daily and everything will be alright. Taking care of fish takes time some times. They will live and thrive for a long period if you take care of them.
Make sure that you do not have too many fish in your tank! Overcrowding the tank might make it look nice, but fish need space and it is not a good idea.

Answer 3

My guess is that it is an optical illusion caused by the light reflecting off its scales as it poos.

Answer 4

The time to worry is if and when they stop pooping. Everything has to poop if it eats. Be happy that your fish are doing OK.

Answer 5

a goldfish's mouth turns red from the food it eats.

Answer 6

Goldfish fins typically become red due to stress or in addition to a disease. Make sure that you test your water regularly to keep the toxins at safe levels.