Why Water Quality is so critical for Koi fish

Koi keeping should be about enjoying Koi! Water quality is the key to enjoying your Koi. Poor water quality with high ammonia levels kill Koi, debatably reduces their coloration and leads to more people giving up on the hobby in disgust. It's a terrible waste of Koi life and your money!

Water quality can't be bought. It has to be maintained! Ammonia has to be removed. There are NO cheap and easy ways of doing it despite the best protestations by some ill advised dealers. Read through this site and make sure YOU and not your dealer, clearly understand the basic principles or else you are setting yourself up for failure, I guarantee it. YOU have to maintain the pond, and YOU carry the responsibility of the health of your Koi.

Koi pond water quality - why?

Koi are big fish. They are easily the biggest fish that can be kept as a hobby. They are also ravenous and fast growing fish. Koi eat just about anything and everything. And they excrete a lot of ammonia.

In fact, Koi produce more waste material (ammonia) than other fish of equivalent size.

But just because they're 'water pigs' doesn't mean that Koi can live in the equivalent of a pig sty. Yes, they are tough as far as fish go, but you must understand that 'tough' is relative.

Fish are "open systems". This means that they are composed of the same water that they swim in. Nutrients, chemical compounds, oxygen, water, mineral salts, trace elements, ammonia, nitrites and so forth are all as integral a part of the pond as they are the Koi themselves.

In other words Koi are constantly, continuously exchanging substances all the time with their pond water. 24 hours a day, 7 days a week, 365.25 days a year. You get the picture.

Thus, if a pond is lacking in a vital element, so too will the Koi. If a pond has an excess of a dangerous compound, such as ammonia and/or nitrites, so too will the Koi.

I am not saying that a Koi's internals will have exactly the same composition as pond water. But I am saying that they will be demonstrably similar.

A natural balance in a dam or lake is much easier to maintain that in a Koi pond because of the lower stocking densities. I'm talking about orders of magnitude that are in excess of 1 000 between a natural dam and a Koi pond. Beyond that there is no point in measuring!

These numbers are enormous. And they are not exaggerated as much you'd like to think. Stocking dams have the highest number of Koi per volume in any natural environment and even these high density dams offer a much higher volume to fish ratio than the most optimistic Koi pond could ever hope to achieve. This means much lower concentrations of toxic ammonia.

What this means is that the slightest change to any water quality parameter is dramatically magnified in a Koi pond by up to a factor of 1000! This is truly incredible - consider for instance a Koi that has a normal meal and excretes its normal waste ammonia into the pond. The concentration of these ammonia wastes is thus 1 000 times stronger than in a dam! I don't care how well evolved you are, that's gotta hurt!

Consider a massive Koi pond with a stocking level of only 10 times that of a normal dam. The changes in water quality parameters are subject to a 10 times variation! Even trying to control a variation of this level of magnitude is going to be difficult - to put it into context this is a 1 000% variation...

So we can see that stocking levels play a critical role in water quality. It is very, very much harder to maintain a natural balance of trace elements, mineral salts, dissolved oxygen, toxins, parasites, bacteria, pH (and yes, ammonia!) and any number of measurable parameters that you care to think of in a Koi pond because of it's limited size. And you thought 10 000l was big!

Water quality in a Koi pond is thus a difficult thing to define. It is virtually impossible to achieve a natural balance as would occur in a large lake. But we can get close and this is ultimately the pursuit of the hobby - to try and attain the unattainable.

We measure our success of that goal by keeping Koi. If they thrive and prosper and live out their relatively long lifespan of 30 years, we know we're good water quality hobbyists. It is my firm belief that only once we have mastered the art of good water quality can or should we start to move on with the hobby in terms of the enjoyment, appreciation and showing of Koi.