Koi Myths

Author: Richard Guest of Pets Parade Team

Every pastime has its share of old wives tales and myths and koi keeping is no exception. Any one who has kept koi for a few years will have heard or read the same old stories doing the rounds. Many of these pearls of wisdom are passed on as "facts" with little thought being given as to their origin or accuracy. Much of the time misleading information does no harm and in a hobby such as ours there are many ways of achieving the end result. Often there isn't just one correct way of doing some thing. But on many occasions received wisdom can be the cause of major problems, expensive for the koi keeper and possibly fatal for the koi. In this article I have listed a few of the more common myths we hear in our shop every year.

A new pond should be run for several weeks before introducing any fish, to let the pond mature.
The filter that is the "heart" of a pond system won't mature until it has a complement of bacteria living in the filter media. These bacteria live off the Ammonia and Nitrite produced by the fish, no fish = no waste products = no bacteria. You can run the pond for weeks or even months but the filter won't start to mature until you add the first fish.

You should never do any water changes once the pond is established because it will upset the "natural balance".
We regularly speak to customers who have been told this by well-meaning friends or even by another aquatic centre! Unless you intend keeping one koi in a pond of several
thousand gallons you will never achieve a natural balance. In a natural lake, the stocking density is a fraction of that in the average koi pond. Each fish has a massive volume of water to dilute the Ammonia it produces and the lake bed teems with bacteria that break down this waste product. There will also be plants and algae that utilise the Nitrates produced for their own growth and anaerobic bacteria that complete the Nitrogen cycle. Compare this
situation with the average over stocked and bare koi pond. It soon becomes clear that nature requires a helping hand in the form of regular small water changes and the removal of solid wastes, as well as a large biological filter. We are keeping our koi in a completely artificial environment so to talk of a "natural balance" is completely misleading.

You must never use Formalin in a pond containing salt.
This is quite a new "commandment" I can remember hearing this for the first time at a local koi society meeting several years ago. This was news to me, as I had been happily using Formalin and Malachite Green to treat parasite problems without any adverse effects in ponds that already contained salt. Neither the person at that meeting nor any of the articles I have read since have ever said why you couldn't use the two together. In the absence of any good reason I have continued to use formalin even when salt has been previously added to the water and have never encountered any problems. It is true that the use of formalin removes oxygen from the water and salt water also holds less oxygen than fresh water. But providing adequate aeration means problems shouldn't arise. If you are still in doubt console yourself with the knowledge that formalin is used in marine aquariums containing a far higher level of salt than any koi pond. Perhaps the fish just haven't read the books!

The airstones in a filter must only be positioned in the transfer ports between the filter chambers, never in the actual media chambers.
We all know that adding aeration to a filter helps to cultivate the maximum number of bacteria that can live in the filter. But the positioning of the air stones seems to a
subject of considerable controversy, according to some people they must only go in the transfer ports between the filter chambers. Apparently, dropping an air stone on the media will dislodge the filter bacteria and reduce
the filters' efficiency. Delicate things these bacteria! I never seem to read any press reports of a koi keeper making his fortune by selling a cheap and effective sterilisation
unit to hospitals to remove bacteria. Just drop your surgical instruments into a bowl of heavily aerated water and they come out with all the bacteria removed! From personal experience I would say that as long as you have aeration in each chamber it doesn't much matter where you
put it. The other worry is that air stones bubbling away in the media will cause tracking of the water as it rises with the column of bubbles, so bypassing most of the media. Quite how a couple of thousand gallons an hour passing through a filter can be diverted upwards and through just a few spaces in a jap' matting cartridge is a mystery never explained.

Adding Tench or other "bottom feeders" will keep the pond clean.
This is such a tempting proposition I just wish it were true. Imagine no more maintenance, no more cleaning dirty filter brushes, just put in a few living Hoovers and let them do all the work. Unfortunately life isn't that easy, no fish lives on a diet of rubbish and the Bottom feeders will themselves add to the waste loading in the water. What goes in one end goes out the other and this is just as true for Tench as for Koi. Faeces, dead leaves and all the assorted debris that finds its way into the pond needs to be physically removed. Either via bottom drains into the filter and then flushed to waste or by use of a pond vacuum. You cannot put any fish in your pond that will do away with the need for regular maintenance. True, Tench will eat food from the bottom of your pond, but then so will koi and goldfish and if there is lots of uneaten food in the pond then you're feeding too much. All you will
achieve by putting such fish into your pond is less space to add another Koi. More importantly if you don't carry out regular water changes and removal of solid wastes, water quality will deteriorate and your fish will suffer.

Finally I would like to mention one other myth I heard recently, but this one has the ring of truth to it.

Apparently if you cross the palm of a koi dealer with silver it will bring seven years good luck, Well worth trying I think!

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