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Healthy Koi Keeping

As a beginner it is easy to get the impression that the skill of koi keeping is knowing how to treat health and disease problems. Not true! While this is often seen as proper hands-on fish keeping, the real skill in any kind of fish keeping lays in preventing health problems. The skilled koi-keeper is not the one with fingers ever stained from applying disease treatments but the person who rarely has fish health problems. If we accept that most problems are related to pond water conditions then we see our main task is to maintain a good and healthy environment for our fish rather than continually applying disease treatments. Regular water testing will help to show when something is amiss but it is important to understand that water test-kits check only a few parameters - albeit very important - and there are other considerations.

We can avoid many potential health problems by regular pond and filter maintenance. Though they may vary in design, the correct general aim for all ponds is to maintain good filtration and to keep the system clear of solid muck. This will provide conditions that are suitable for beneficial micro organisms while discouraging undesirable, opportunistic organisms.

New pond syndrome

The most important part of a pond is the filtration system. This keeps water clean, clear and free of toxins such as ammonia and nitrite that are produced directly or indirectly by the fish and from decaying organic matter in the pond. Efficient filtration relies on the presence of beneficial micro organisms such as bacteria, algae and protozoa. However, it takes a while for some of these organisms to become established in sufficient numbers to be fully effective. During this time water quality may be less than perfect, creating a situation commonly described as 'new pond syndrome'.

While the filter is maturing it is most important to make regular checks on water conditions and, if needed, carry out water changes, reduce or stop feeding and limit stocking levels. It is also advisable not to use a UV lamp for the first six weeks, as UV radiation will kill bacteria including nitrifiers. It can be useful to have some zeolite available if ammonia levels increase but only use it as an emergency measure, not permanently. Simple nitrification can be established in 4 to 8 weeks in our tropical climate, but full maturity of the filter can take a whole year.

Stocking levels

A major consideration is stocking. Most problems experienced by beginners are related to overstocking. It is natural and understandable to want to fill the pond with your beloved fish - after all, that's why you spent so much time and money on building the pond. But as stocking levels increase so must the skill and experience of the koi-keeper. By increasing stocking levels we progressively reduce the margin between good and poor conditions. In doing so we move away from the ‘balanced’ garden pond towards an intensive fish culture system that relies heavily on good ‘management’ to keep problems at bay.

The stocking potential, measured by the mass or weight of fish rather than number, of a pond is determined by pond volume, filtration capabilities and - one of the most important criteria - the knowledge and experience of the pond keeper. It is all too easy for beginners to stock beyond their capability, reaching a point where the system collapses and disease starts to spread. This is the proverbial straw that breaks the camel's back. Be patient and increase stocking levels slowly so your system and your knowledge can keep pace with one another. This way, it becomes a pleasant, relaxing hobby rather than a constant stressful upset.