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Black Patches On A Pond Goldfish

Guest Kaos

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[*]Test Results for the Following:

[*]Ammonia Level? 0

[*]Nitrite Level? 0.25

[*]Nitrate level? 0

[*]Ph Level, Tank (If possible, KH, GH and chloramines)? unknown

[*]Ph Level, Tap (If possible, KH, GH and chloramines)? unknown

[*]Brand of test-kit used and whether strips or drops? Aquatics centre, drops

[*]Water temperature? Cold (it's outdoors - and colder lately)

[*]Tank size (how many gals.) and how long has it been running? Pond, 150gal, two months

[*]What is the name and size of the filter(s)? Filtral 2500 UVC

[*]How often do you change the water and how much? Haven't so far.

[*]How many fish in the tank and their size? 5 goldfish (4 common, 1 Shubunkin), all around 5-6cm

[*]What kind of water additives or conditioners? None

[*]What do you feed your fish and how often? Every other day (for the last week - previously, every day), flakes. Bloodworms once a week.

[*]Any new fish added to the tank? Four of them added three weeks ago.

[*]Any medications added to the tank? No.

[*]Any unusual findings on the fish such as "grains of salt," bloody streaks, frayed fins or fungus? Black patches & spots on one.

[*]Any unusual behavior like staying at the bottom, not eating, etc.? No.

This is referring to a smallish garden pond (150gals/630l) that was set up a couple of months ago. After two weeks with the plants and filter set up we added two goldfish. They did fine, so two weeks later we added four more goldfish - I would have quarantined them, but didn't have a tank set up yet. One of the first two goldfish died last week after (probably) getting a bacterial infection... by that time i did have an isolation tank ready and removed it when it stopped eating, and the other fish all seem fine since then.

However one of the four newer fish had some small black spots on its face when I got it. After doing some reading I expected it was ammonia burn and would probably fade. But since being in the pond it's gained an increasing number of spots on its body, and just recently black tips on its fins and a large splodge on one gill. I had the water tested last week at an aquatics centre - the guy said ammonia and nitrates were 0, though nitrites were 0.25. He recommended feeding them every other day instead of every day, which I've been doing since then. Unfortunately he didn't tell me anything else, though I presume this means the other readings were okay. I'll be looking to get my own test kits soon.

Meanwhile, if ammonia's 0, what could be causing this? Can it be natural colouration, or should I be taking more drastic measures like water changes or isolating the fish? I read about 'black-spot' parasites though it doesn't sound too likely.

Thanks for any help!

PS: The affected fish behaves normally, as do the others. I've noticed one black spot on one of the other fish - the remaining one of the original pair I bought. One of the others is a Shubunkin and has always had a couple of very tiny black spots - these haven't changed at all.

PPS: The pond has a good number of various plants in it (marginal, oxygenating, floating) and the water is very clear.

Edit: Hello by the way! I think I'm becoming a bit of an enthusiast, nice to meet others that feel the same way. :)

Edited by Kaos
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  • Regular Member

Hello and welcome to Kokos! :exactly

Ammonia burn is a funny thing because it is delayed. It is a process of cell renewal (melanaphore migration) that involves time, usually a week or a few weeks to show up. Sometimes the blackening can keep on arriving for quite some time as the fish goes into a very slow kind of allergic reaction. It is possible this is leftover reaction from the store you bought the new fish since it is just within the time frame.

However, I think it is actually more likely that the tentative cycle you had with the other fish in the pond for the first 2 months was unbalanced by the new fish editions and ammonia peaked when you didn't know. The nitrites are telling here as these are the end product of stage 2 of the nitrogen cycle and indicate that ammonia must have peaked in order for them to be peaking...

I suppose the plants are keeping the nitrates at zero. I would still want to have my own test kit to know exactly whats what.

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  • 3 weeks later...


Thanks for the help, Trinket! Little Yellow still has the black patches, but no worse. The other fish with a black spot had its dorsal fin turn black-streaked quite soon after my first post, but that's all.

I got some water-testing kits of my own at last; pH 8.0, Ammonia 0.1, Nitrite 0.1, Nitrate 75

So that's a relief. The pond plants are quieting down for the winter now - I'll do a partial water change to help with the nitrate. The fish all seem happy, so I'm relieved. :)

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hi there! and welcome to koko's

see if you can do a larger wc, ammonia & nitrites should be 0 and NitrAtes should be around 10-15.. you will find that your fish will continue to receive nitrate burns at that level.. so the experience of black spots most likely will reoccur :(

the only way to reduce nitirates unfortunately is back to back water changes say 3-4 water changes of minimum 60% each..

best of luck to you..

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