I've had this goldfish for around 2 years now, and have no problems with it at all. I changed it over to a bigger tank (22 litre) around 3 to 4 months ago, and until now have had no issues. The tank has NO other fish within it, and just some standard plastic trees and gravel.

Every 2 weeks I change the water (around 25%) and also use "fish safe" water conditioner to try and remove some of the impurities within the water. I also use a manual vacuum to clean the fish gravel.

I'm unsure whether I've just not noticed, or whether this has happened in a small time frame, but the back fin on my fish is starting to look a bit ragged.

The other fins appear to be fine; I thought the black marking may have been a sign of poor water quality, but they seem to have been like that for over a year now.

Additionally, it seems to be swimming in one corner of the fish tank, which is very unusual for this fish as he/she is usually happily swimming around the whole tank.

I have given it some "disease safe" product, but as I'm unsure whether this is an actual issue, I don't want to overload the tank with lots of chemicals it doesn't need.

I've attached some images below to help clarify what I'm referring to.

Would any fish/pet experts be willing to offer some advice?

Close up of fish fin

Fish Image 1

Fish Image 2


  • 1
    take a water test and post the readings ammonia-nitrite-ph-nitrate.your fish do have finrot but this is a result of not cycling your tank properly before you add the fish,please take a look here on how to cycle a tank fishlore.com/NitrogenCycle.htm and do not use any medication in your tank. Aug 8, 2019 at 19:01
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    Interesting. I followed the instructions on allowing the water to flow through the filter for a day or 2 before putting in the fish but I'm guessing this isn't the same thing. I can't purchase a water testing kit until tomorrow as all the shops are shut, but will do so in the morning and post the results. Is there anything I can do in the meantime or is it best to leave the fish in the tank undisturbed?
    – Josh
    Aug 8, 2019 at 19:12
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    i will try to make an answer later today,but adding some aquarium salt might be usefull to lower the toxity of nitrite to your fish use a consentration of 0,3% this is safe for goldfish and other fish in the carp family. Aug 9, 2019 at 3:43
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    Thanks, I am intending to go out and buy some First Aid Salt and Anti Fungus & Finrot treatment so hopefully stop this.
    – Josh
    Aug 9, 2019 at 8:34

1 Answer 1


Your fish does have finrot. The cause for this is often poor water quality as a result of a build up of ammonia or nitrite in the water.

If a tank is not properly cycled, you will not have the useful bacteria that convert fish waste into nitrate (plant food). Please take a look here on how to cycle a fish tank.

To kick start a tank you can use the filter from an old tank and run this for a couple of weeks to seed your new tank.

First aid against nitrite poisoning is to add 0,3% of aquarium salt. Most fish in the carp family (goldfish/koi) will handle this concentration with no problems.

Be very careful in using medication in your tank as most types of medication will kill all the bacteria in your tank. This means you will have to cycle your tank again.

To avoid this, you might set up a hospital tank so you can treat only the fish that is ill and not destroy the biological balance in your main tank.

A 22 liter tank is too small for a goldfish. A minimum tank for one single goldfish is 60 liters and a larger tank will be easier to maintain with less fluctuations in water quality.

  • 1
    I have performed a water test and found that the Nitrite was at the correct level of 0, but the Ammonia was around 2mg/l (ppm). I have done a small water change, and added in some live cleansing bacteria to help break down the Ammonia & ammonium. The advisor at the store has said that I likely didn't cycle the tank correctly, and would have had high ammonia levels when I put the fish in. He had said that he feels after the water test results, that after 3 months the level should drop back to normal levels with the help of the cleanser and the fish is fortunate to have survived the 3 months.
    – Josh
    Aug 9, 2019 at 16:28

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