Introduction To Bacterial & ulcer diseases of goldfish & koi Fish

The descriptions of the common fish diseases have been deliberately kept simple to assist the understanding of the basic problems that may be encountered. This is a fascinating aspect of pond keeping and massive amounts of resource for further study can be found across the Internet.

The key to disease control is observing gold fish or koi behavior. Any lasting changes to normal behavior should be investigated because this is the first indication that something in the pond might be wrong.

A correct diagnosis normally needs more in-depth examination often using a microscope.

Bacterial Infections:

Bacterial infection within fish shows itself as one of the following normally ... reddish lesions in the body or fins, swollen eyes, red mouths, red stomach region, unknown death reasons. The result of bacterial infection is normally septic wounds such as ulcers.

Antibiotics find a place in the treatment of koi or gold fish but this is best done under close and expert supervision bearing in mind that bio filter operation will be severely compromised. It is often best to treat the gold fish or koi fish in a separate bath rather than in the fish pond itself ... in hospital as it were.

Bacterial infection often results from initial infections by parasites of various kinds and also poor pond water quality in general which in turn creates further opportunity for parasite growth. This should emphasize the absolute importance of good pond bio filtration accompanied by regular cleaning of bio filter media along with the avoidance of bacteria traps such as the sand in sand filters. Always remember the critical importance of aeration in well cared for koi or gold fish ponds.

Bacterial infection in gold fish or koi ponds can be avoided to a great extent by using modern products such as Koizyme (previously Lymnozyme)also called Genesyz in the UK. The process of competitive exclusion ensures that Aeromonas and Pseudomonas in particular are starved out of existence rendering the gold fish or koi safe from attack.

Ulcers which are an indication of advanced bacterial attack can be caused by damage to the skin from parasites or exposure to high levels of ammonia or nitrite and/or high or low pH ... bad water quality. Under these circumstances bacteria thrive and the induced stress levels make the gold fish or koi disease prone.

If a single gold fish or koi is affected then that individual may have a specific problem. In the case where numerous gold fish or koi have the disease then there must be underlying problem within the pond.

Please also check out this UK Pond Doctor site for more of Ben Helm's articles

What to do if you suspect disease problems

Test for Ammonia, Nitrite, and pH at a minimum, and preferably also test for Total Alkalinity and possibly Hardness.

Ammonias are lethal in their own right and worse at higher pH. If dead fish exist this will also create ammonia problem. pH can change overnight if the system loses its buffering capacity (this would show on a test of Total Alkalinity)

Aquarium Pharmaceuticals basic drop type test kits are most accurate according to experts. Review USA on-line pond supplies

In the case of Ammonia accumulation:

If water quality is suspect begin a systematic daily changing of 20-40% of the total volume in the system. But beware of major temperature changes the system. A small addition of salt at .1% level will do no harm.