This Koi pond filtration lark is not as simple as we think it is and perhaps them there crafty Japanese Koya breeders have done it right for some decades now?

I think we can all accept now the fact that a re-circulating (man-made) pond filter system requires both mechanical filtration and biological filtration.

The filter system needs mechanical filtration to rid the water of visible debris and biological filtration to process the (dissolved) ammonia that’s constantly given off by the Koi, and these two stages should preferably be kept separate from each other in order to keep the maintenance required as thorough and as rapid as is possible.

BIOLOGICAL FILTRATION.

The dissolved ammonia constantly produced by the Koi, together with the movement of the Koi is present at all water depths.

Whether we take this into the biological stage from the pond base, mid-water or surface water has no importance at all – just as long as this toxic water supply is constantly passed to the media surfaces for processing and removing the toxins.

MECHANICAL FILTRATION.

This is a separate and far more complex matter, but before investigating this matter in greater detail, I think most of us will agree that in these enclosed re-circulating systems; partial and regular water changes are vital.

Not only to replace the water to top up the system after discharges have been made, but more importantly to ‘freshen up’ the water already in the system.

Moving back to mechanical filtration, much of the debris that requires removal in an outdoor system consists of fish waste, leaves, pine needles, twigs and suchlike. The vast percentage of this unwanted matter is taken to the pond base.

(In indoor systems, this problem is not nearly so bad).

However, in both these cases, the most efficient method of removing it all must be via bottom drains and taking it directly to waste.

Some use standpipes and others use valves for this – either way produces exactly the same results.

Once this unwanted matter has been removed, a trickle of fresh water can be used to replace it and also carry out the partial water change.

In the Japanese breeder’s indoor systems, all pond drains and filter drains run directly to a discharge box and are stopped by standpipes for daily removal to waste.

I’ve stood close to a few of these discharge boxes when the drains are being discharged – it is not only debris that’s being removed because the smell is disgusting – believe me, it’s NOT ammonia!

(The ammonia-laden water enters the biological stage in these breeders systems via an open ‘wall feed’ at mid-water depth).

In short, these systems have one method of dealing with mechanical waste that’s kept completely separate from the biological stage.

However, most pond systems in other parts of the world today use other methods of getting the pond water into the filtration systems.

Most gravity-fed systems get water supply directly from the bottom drains and most pump-fed systems get water supply via a pump that’s placed on the pond base.

Of course, this results in all mechanical waste plus the foul-smelling water and the toxic ammonia to enter at the same time, which makes it completely impossible to separate the mechanical stage from the biological stage!

The mechanical filter stages available today are many and varied but all allow some debris to pass through and not one of them can possibly stop this foul-smelling water from passing right through and going straight back to the pond.

As to what this foul-smelling water actually is, I really do not know but I do know that all fish species give off pheromones as a growth inhibitor to smaller fish.

People who grow Koi for a living are well aware of pheromones and the dangers of allowing them to remain in the pond water.

I’ve recently met a Koi breeder who changes 80% of his water THREE TIMES every fortnight simply in order to rid his water of pheromones and put much more growth onto his stocks!

Thankfully, the breeder in question does not have to pay for this water.

The problem of ‘smelly water’ has been getting up my nose (pun intended) of late – so I’ve decided to conduct my own experiments on the subject.

Many out there will already know of my indoor system by now, but for those who do not know – here are the main details.

The system holds 550-gallons, it’s rectangular in shape with a single bottom drain on the base that is stopped by a 2” ball valve.

I have a small submersible pump on the base of the pond and this pumps pond water into my pump-fed Compact Eric filter.

The flow-rate through the filter is 350gph and I have a constant trickle of mains water entering the pond.

The pond is heavily stocked and the Koi need feeding – often.

Being an indoor system the only solids going into the filter consist of Koi waste.

This ‘smelly water’ is not detectable when one walks into the filter house – but open the 2” valve on the bottom drain and then hold your nose for a few seconds!

And that’s all it takes – a few seconds – after that, the water and waste coming out has no smell at all.

My opinion is that this smelly water is only on the base of the pond?

Now I’ve decided to open the valve for a few seconds every morning, even this small amount of labour could be saved by placing a 2” auto valve and timer to the drain line.

In order to simulate a side feed to the filter, I have raised the pump up to mid-water.

I reckon by making these few tiny amendments – I can now –

1. Eliminate ‘smelly water’ completely.

2. Thus grow the Koi more quickly.

3. Reduce the amount of waste going into the mechanical stage.

4. Thus reducing the maintenance periods.

5. Still retain the same vital water changes.

Shouldn’t we all be ‘assisting’ our filter systems instead of expecting them to do the impossible?

I have only been carrying out this new regime for two days and the results seem to be ‘promising’.

The clarity has improved, the brush box remains clean and the Koi appear to be happier.

Why not try out this regime on your own system?

Waddy.