Fin Rot is a common bacterial disease of fish kept in low quality water conditions. It can also affect the gills and tail.
It is caused by gram negative bacteria which eat the delicate membranes of the fish. The damaged area will usually become opaque and white before being eaten away by the bacteria. On top of this fungus will often develop giving the wound a fluffy appearance. It can be easily treated if caught early and the fin may grow back if it is not too badly damaged. If left untreated the fish will probably die.
Tail Rot - appears initially in the tail (caudal) region
Gill Rot - appears initially in the Gill region as white patches.
This bacterial disease which is most often seen in koi and Aquaculture, can also occur in natural populations.
Symptoms of fin rot
The first signs of the disease to look for are milky white areas that appear in the fish? fins or tail, particularly around the edges.
The fins then begin to develop a rather ragged appearance as the disease starts to eat the tissue.
Eventually the disease will eat all the clear fin membrane away, leaving just the fin rays.
If the fin rot has affected the fish? tail (also called tail rot), it may work its way through to the body of the fish.
The development of secondary infections or diseases are common in advanced cases of fin rot, and these will bring new symptoms to the affected fish such as white cotton wool-like tufts or streaked patches of red.
If you catch fin rot early enough you can treat the root causes and let the fish take care of itself, which is always better than treating the whole pond.
Causes of fin rot
Fin Rot is caused by a bacterial infection. It is thought likely that there are several different bacteria that cause similar diseases, Flavobacterium columnare (previously known as Flexibacter) is most often blamed, however, Aeromonas and Pseudomonas have also been mentioned.
It is not correct to say however, that the bacteria cause the Fin Rot. If fish are weakened by physical damage, been attacked by parasites or stressed due to being kept in poor conditions, bacteria can take advantage and move in.
Fin Rot is not particularly infectious to other fish, and is usually only seen in one or two fish at one time. This therefore adds to the belief that a weakened immune system is the trigger in the disease taking hold.
Treating Fin Rot
There is a three-step program to treat Fin Rot successfully:
Fixing the environment
Treatment with a propitiatory anti-bacterial agent
Fixing the environment
This is the first and most important step, after removal of the infected fish. It is no use treating the fish if you are then going to return them, and continue to expose others, to the same environment.
Do a couple of 20-50% water changes using clean, aged water if possible. Remove as much debris from the bottom of the pond as you can and check and clean all filters.
If the pond is overcrowded you will need to remove some fish if at all possible, but obviously it would be better if you had the correct ratio of fish to water area in the first place.
Using an anti-bacterial treatment
There are various propitiatory anti-bacterial treatments available and these are effective against fin rot if caught early enough, examples are Melafix or Acriflavin. Adding a level of salt to the water is a good mild treatment if the species of fish can tolerant it and the above are not immediately available.
Remove the affected fish to a clean quarantine tank with a simple filter system, rather than treating the whole pond, which although safe would be more expensive. Propitiatory fish treatments should not affect 'good' filter bacteria if they are used at the proper dosage levels and according to the manufacturers instructions.
Treating with antibiotics
In the USA it is common and acceptable to treat fish with off-the-shelf antibiotics.
As mentioned previously if you catch fin rot early enough and you should? need antibiotics anyway. Which is better for your pocket, the fish and the environment.
Preventing fin rot
Fin rot can usually be prevented by keeping your pond in good condition, as discussed.
Be sure to set your pond up properly. Once running, check that it is sensibly stocked, and that you? 1) doing regular water changes (at least 25% a month, and ideally 10-20% a week). 2) Think about choosing a new filter if you know the one you have is inadequate or needs replacing.
3) Make sure that your fish have the best diet possible as this plays a vital part in keeping fish fit and healthy. 3) Feeding a wide variety of foods is recommended and make sure that all fish have enough to eat.