Goldfish turning black

Goldfish turning black in patches on body and fins

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Goldfish turning black within a short time indicates either ammonia or carbonate mineral (KH) poisoning. We say ‘poisoning,’ however, fish are actually burned by ammonia. Whitish marks first appear when the burns are fresh, although, they later turn black as they’re healing

Burns cause inflammation of the gills, leaving the fish at high risk of oxygen deprivation also

Uneducated fish keepers unknowingly burn their fish repeatedly because they are unaware of the nitrogen cycle. Ammonia, the first toxin to form in the nitrogen cycle; created from the waste goldfish produce. When present, beneficial bacteria form to feed on the toxin converting it to nitrites and then into nitrates, the third and final toxin to be converted in the cycle. Both toxins are closely related, because they are both created by living organisms, although both can be just as dangerous as ammonia

Goldfish black patches

New goldfish keepers are unaware of the nitrogen cycle; unaware of the risk of ammonia poisoning. The first symptom to appear are clamped fins. This becomes obvious as fish pull fins close to the body in an effort to reduce the severe pain these toxins are capable of

Koi turning black

Goldfish change colors as they mature. Black fish turn white. White fish turn black. It’s easy to tell a natural color change, because unlike poisoning, it takes time; month or even years. Burns however, take a only few short weeks to turn from white to black

Test for ammonia

goldfish turning black
Goldfish turning black

Sick goldfish live in sick water due to ignorance, however, perform this lifesaving water change, and you’ll see an amazing difference in the water, and your fish also

life saving water change

Refer to:

10 Steps Goldfish Koi Keeping

About Ammonia


Aloe Remedy

Oop Boost

Back to symptoms and ailments

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Author: Brenda Rand


By Venus

Master goldfish keeper