What matters? Clean or Clear?

Today I'm going to briefly discuss what is important about filtering your pond water.

Most people come to my web site to cure a "green water" problem in their pond. Actually green water is not necessarily a bad thing, but it can be an indication of more important problems. Green water is in fact simply nature trying to bring the ponds eco-system back in balance. But usually people want to get rid of the green water because it is unsightly and they cannot see their fish. After all what's the point of keeping fish if you can't see them?

So your concerns are more on an aesthetic level initially. You want clear water. Well that's fine. Yes of course you want to see your fish again, but you need to realise the more important reason for filtering your pond water.

Clean water is more important than clear water!

A biological filter is quite simply the heart of a koi pond. It is not essential in small fish ponds, but the more fish you stock, the larger they get and the more they eat, so the need for a bio-filter becomes greater. The pond gets to a point where it needs a "sewage farm". It's purpose is to convert the waste matter produced by the koi from harmful ammonia into less toxic waste.

It is less important to remove solids particles from water than it is to process nitrogen, so if there is to be a compromise between mechanical and biological, err on the side of biological.

In other words, it is much better to allow sediment particles below a certain size to escape back into the pond, while converting a great deal of ammonia to nitrate, than it is to catch every little thing down to a micron or less which in the process would slow the water down to the point where the bacteria have a hard time living (because they're not getting enough oxygen).

The bacteria that convert ammonia to nitrate for us are among a class of bacteria that you may have heard of before. They are the so-called, “nitrogen fixing” bacteria. This means that they take nitrogen that is unavailable to plants in its ammoniacal form, and make it available to plants in an oxidized form.

These are the same bacteria that live among the roots of leguminous plants. Without these beneficial bacteria, life as we know it would cease. So be kind to your bacteria. What they need to survive is a large surface area, chemically inert medium and a ready supply of fresh water. They depend upon dissolved oxygen in the water to live and to do their job. As soon as the water flow is stopped, the oxygen in the filter becomes finite, and eventually gets used up. The ultimate result is that the bacteria die, and you have to start over.

By using and maintaining a bio-filter to keep it in good running order you are ensuring that the water in your pond remains clean.

And the by-product of having clean water will in time result in clear water, and happy, healthy fish.