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Fin Rot and How to Treat It

21st Nov 2019

If you’ve noticed inflamed red patches, faded colour on fin tips, frayed decaying tissue around the mouth, fins or tail, then it could be that your fish is suffering from fin rot. Fin rot is a bacterial infection that can be caused by a number of things - such as stress, poor water quality or an over population of fish. Any of those issues can cause a weaker immune system in your fish, so making them more vulnerable to bacterial infections. If left untreated this condition can progress from the edges of fins or tails destroying more and more tissue until it reaches the base. It can also make your fish lethargic and cause them to lose their appetite.


First, move any affected fish to a separate holding tank (sometimes called a quarantine tank). Add an antibacterial treatment to the water such as Bradshaws Make Your Fish Healthy Pond Treatment or Interpet Anti Fungus and Bacteria Fish Treatment. At this point it’s also good to make sure there is plenty of circulation and aeration in the water. This can easily be accomplished by use of an Air Pump. Next you could add a Stress reducer product such as Pond Protector Tonic Salt. This will generally reduce stress and lead to faster recovery.

Now you need to eliminate the bacterial infection form your existing pond, so it’s a good idea to test the water first for levels of Nitrite, Nitrate and the Ph Levels and correct as necessary. The Tetra Quick Test 6 in 1 Pond Test Kit is great for that.

Clean out any decaying plant matter, debris or sludge from your pond by use of Nets or Vacuums. Add some aeration to the pond with an air pump, fountain or other water feature (if you already have these check they are clean and working to full capacity and if possible boost their power). You may also want to do a 20 to 50% Water Change.

Prevention is better than cure

Once you’ve rid your pond of that nasty bacterial infection you need to ensure it doesn’t come back (remember prevention is always better than cure).

First check that your pond is not likely to still provide an environment that might facilitate fin rot and other fish health issues. Do you have enough filtration and aeration? Are there too many fish in your pond? Are you feeding your fish too often? To remedy these issues add to or improve your filtration or aeration equipment where necessary, find new homes for any fish that are causing overpopulation and perhaps limit feeding to one time per day. Remember shading a part of your pond or adding a fountain, waterfall or other feature are good ways to increase oxygenation in your pond also.

You might also consider adding beneficial bacteria to the pond, with a product such as our Bacteria Bio Bullets.

Follow these simple tips and you should be able to keep your fish happy and healthy and free from fin rot and a host of similar conditions.