You may have read that it is advisable to turnover the entire volume of water in your pond every hour which might not be feasible in a larger pond. It is vital to turnover the water in your pond at a sufficient rate to remove ammonia and nitrite from the water. But what is that rate?
Think before you increase waterflow
If you are fortunate enough to own a large koi pond, turning over the water every hour would require an impressive filter system and truly scary energy consumption! Before you plan to construct your own power station, it is important to consider that issues with nitrite and ammonia are less common in larger ponds.
The smaller the pond, the more likely it is to be overstocked and the harder it is to keep the water quality stable. Larger ponds can sustain slower turnover rates and you will probably find that a turnover rate of 2-4 hours is ideal unless your pond is enormous. You can test your water regularly using a proprietary kit but if you do discover ammonia in the water, merely speeding up the turnover rate may not help and might actually prove to be counterproductive.
Is your pond filter too small?
Poor water quality would most likely be the result of a using a filter of insufficient size. Speeding up the water flow will merely result in the pond water passing too quickly through the filter for it to process it properly.
Bear in mind that your pond's surface, walls and floor will be colonised by the same bacteria that feature in your filter. The larger the pond, the larger the surface area, giving you a bigger bio-filter. Turning up the flow may achieve nothing more than a huge electricity bill!
In larger ponds, poor water quality will usually be the result of inadequate filtration or overstocking. Attend to these potential issues before considering adjusting the turnover rate of the pond. It is possible to achieve outstanding water quality in a 30, 000 gallon pond, for instance, with a turnover rate of 16 hours, providing the filter is up to the task.
Why does inadequate filtration time promote algae growth?
It is the breakdown of dissolved organic carbon compounds into simple inorganic compounds which is the most time-consuming aspect of filtration. The resulting compounds are ultimately incorporated back into living organisms.
This complex process is never instantaneous and will, even under ideal circumstances, take some time. It isn't hard to see that if insufficient filtration time is available, intermediate products will be pumped out of the filter back into the pond. Which rather defeats the object of having a filtration system! Inadequate filtration often leads to excessive algal growth occurring because the filter is merely producing a generous supply of plant nutrients!
You have a delicate balance to strike if you are to achieve optimum water quality in your koi pond. It is possible to indulge in complicated calculations but ultimately, trial and error might be the only way to find the perfect combination of filtration, turnover and stock levels.