Biological Koi filters incorporate two stages of filtration. The first stage is the settlement or entrapment section of the filter. Solid organic matter is dragged into the settlement area by way of gravity and current produced by a pond pump, waterfall or fountain, which aid in the circulation of the pond water. Now being that the settlement area is the first stage of filtration, it has to be very efficient at it's portion of solid waste collecting. The desired end result is good clean healthy water for your Koi. For the filter to produce such clean water, very little solid waste can be allowed to enter the biological section of Koi filters.

The conditions required in the biological section of filtration are the support and productivity of hearty growth among the nitrifying bacteria occupying the filter media we have provided there, while at the same time keeping conditions that promote the development of heterotrophic bacteria isolated to the settlement section. This division allows for the break down of ammonia, into the less harmful compound nitrate, to proceed efficiently by the nitrifying bacteria. So the more efficient the settlement are is at collecting and removing solid organic waste from the incoming water, the better the biological section will be at converting dissolved pollutants into less harmful compounds, thus giving us our desired result of good, clean healthy water produced by Koi filters.

Nitrate at low levels is good for your Koi, however it is also good for algae as nitrate is a prime food source for them. There are two types of problem algae to deal with in Koi ponds, green water algae and blanket weed algae. Green water algae are just as their name suggests. They are microscopic algae in the pond water that turns the water green. They pose no direct health threat to Koi and are actually beneficial to them. You see, Koi eat the invisible algae, which enhances the Koi's colour. However, during the warmer summer season, green algae use a substantial portion of oxygen in the pond water. This could leave your Koi struggling with the deplenished amount of oxygen left.

Vegetable filters are a natural way of getting rid of green water algae. If you have plants in your pond then this will help, as plants would use the nitrate, leaving the green algae with little to nothing to survive on. Biological Koi filters, which include UV (ultra violet) filtering, are also highly recommended. Pond water passing through the filter is also passed through a UV filter which kills the green algae. The dead algae become part of the trapped sediment in the filter to be emptied and cleaned later. The clean, clear water is passed back into the pond. Not so popular are algaecide chemicals. These would require routine and consistent use, as the problem would recur. In contrast, the use of magnets placed on the filter pipe would internally alter the algae cells either killing them or keeping them from reproducing entirely.

Blanket weed is a different kind of problem all together. Blanket weed algae are filamentous algae. It grows in long green strands attached to the pond walls. It does not pass through Koi filters to be dealt with by UV filtration. Although blanket weed poses no threat to Koi, it is simply unsightly. One benefit of blanket weed is that it also uses up nitrate, which stops green water algae producing.

To ensure the best possible natural environment for your Koi, always maintain your filtration system with routine cleaning. The reward of healthy Koi thriving in your pond is well worth the effort of keeping their water pollution free.