Black Discoloration

[Gemmylou]

I have been given the job of cleaning my nans goldfish when I go over to her house. This week I have noticed a black discolouration on the dorsal fin and gills. Any ideas what it could be? I have a feeling its fungal? I have no water stats as it's my nans fish.

Gem

 

[WILDER]

Black patches can be ammonia burns that are healing.

Size of tank in gallons or litres.
How many fish and which type.
You need to tell your gran to get her water tested. Can you do it for her.

 

[Gemmylou]

I know its a 20 litre tank
with one goldfish in it
and a small one at that
I can test the water as i have my own tropical tank but not until i go see her
So if i can get the ammonia under control he should be ok?

Gem

 

[WILDER]

The tanks to small.
What type of goldifsh is it.

Common goldfish need 20 gallons for the first one. Then a 40 gallon filter.
Fancy goldfish 15 gallons for first one. 30 Gallon filter.

Goldfish are massive waste producers.
I would rehome the goldfish as it will just die of ammonia and nitrite poisoning.

 

[black angel]

the blackening is the fishes skin healing from the ammonia...please test the water for ammonia and as soon as it rises change the water. from this you will know how regular to change the water...i do agree though that he does need a bigger tank.