Goldfish Covered In Black Coating?

[Guest rt1984]

Hello. I had two goldfish until this morning when I have only one. They have been in the tank for 3 weeks total. The one who died had spent the last 2 weeks turning a black colour. I thought this was ammonia burn so I changed the water 50% twice in the two weeks and added some water treatment to normalise nitrates & ammonia levels. Today I found the fish dead and upon removing him from the tank found that the colour actually rubs off the fish - so it wasn't changing colour (as the pet shop suggested), it was covered in something black. I have a 30L BiOrb.

The other fish is now showing black patches and sometimes 'twitches' a little.

Any help you could offer would be most appreciated.

Edited October 10, 2010 by rt1984

[Kateana]

I believe 30L is equal to about 7 gallons...not sure..

Either way, your issue here most likely is Ammonia burns. I've never heard of it "rubbing off" but with a aquarium that small and overstocked, it's more than possible. How long have you had the tank up and running? Does it have any gravel? How often/how much water do you change? Sorry for the barrage of questions. I just need more information on your situation. The advice I would give to you right now is to get your remaining goldie out of that tank and into a large container, like a big tupperware bin, as big as you can find. Anything with more room than your BiOrb. Try to get a filter set up in there and add some Prime or Amquel to take care of the Ammonia/Nitrate and help the fish with his slime coat. More members should be on their way soon to offer more helpful advice! First thing's first though, your goldie has to get out of that 30L.

Edited October 10, 2010 by Kateana

[Trinket]

This will be ammonia burn plus pH problems combination. The black ammonia burn/melanophore migration happens on the slimecoat which is the slimy top epidermal layer of the fish. So when it comes off it sloughs off as you say just like a coating.

Slimecoat comes off when pH drops below around 6 OR when pH changes up and down too fast.

Blackness occurs a week or so after a fish is exposed to ammonia.

3 weeks in a new tank with only 2 50% water changes, your ammonia must have gotten very high. Do you have ammonia and pH test kits? They really are worth investing in as water control is key to getting you through the nasty first 6 weeks of the eco system setting up. The nitrogen cycle. This happens naturally if you change out water when ammonia reaches 1 and keep doing that for around 5 to 6 weeks on average. After that your tank is safe and you can monitor less often and do those once weekly 50% changes.

[Kateana]

[Captain Findus Goldfish]

Oh dear... I have a BiOrb but not even my Betta had enough space. Do you have the possibility of getting them a proper tank or a rubber tub? They also need proper filtration of 10x the size of the tank per hour. Each goldie needs 60liters of water.

[Guest rt1984]

Thanks for the replies everyone. I bought some disease treatment and put it in the tank with the remaining goldie, and he seems to be brightening up a bit - still has black marks on his head though. Hopefully these will fade in time.

Thanks for the responses, it's a great community you guys have here.

[Cynders]

What medication did you put in the water?

[Captain Findus Goldfish]

you really don't need medication. just clean water.