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Chris on Koi

Water Restrictions and Koi Keeping

Although we are in a drought situation our climate in South Africa has been variable over many years. We have periods of drought and periods of good rains. Do you remember 5 years ago the amount of rain we received? I recall my driveway collapsing where the ground was water logged and the bricks just sunk into the ground. Remember 10 years ago – well the spruit near us was a raging torrent. My koi pond overflowed like a water fall. I had to build diversions at the back of the property to guide rain water way from the pond area that ran into the property from the house next to me. Ponds on the West Rand had so much rainfall that the pH of large ponds was altered significantly. The rain was falling at a low pH of 4.5.
In South Africa we have entered a phase of drought and water restrictions. So what do koi keepers do? We can’t put our heads in the ground and ignore the current situation.
                                             Head in sand

In recent years KZN has had water shortages and restrictions. It is nice to know that very recently water restrictions have been lifted in Balito - after two years of severe water restrictions.
In parts of California, America have had severe drought for several years. There were conservation measures put in place. Basically everyone was asked to reduce their water consumption by 25%. So homeowners removed lawns and replaced them with drought tolerant landscaping.

Recently a lot of rain has fallen in Northern California, the dams have begun filling and this has relieved the situation somewhat with water restrictions being lifted. We know that the Vaal dam is 30% full at the moment – but the Vaal Dam is part of a much larger scheme and is deliberately kept at a low level because of its large surface area.  It is a high evaporation dam. Water is supplied to the Vaal SAM from the Katse Dam in Lesotho and water is stored in the huge and deep Sterkfontein Dam which is at 89% capacity, at the moment – down from 97% from last year. Water from the Sterkfontein Dam is released once the Vaal Dam drops to below 16%.
A bit of trivia – the Vaal Dam has a shore line of about 800 kilometres with a surface area of about 320 square kilometres. It is the 4th largest dam in South Africa but supplies the most populous and industrialist area of South Africa. It has its own 5 km long island in the middle of it.

The dam was severely tested in February 1996 when the largest flood ever recorded at the Vaal Dam was experienced. An inflow of over 4,700 cubic metres per second was measured into the Vaal Dam which was already at full capacity due to good rains. And one time the Vaal Dam was 118% full and great concern was voiced about the dam wall – but it stood up to the floods.

A bit a trivia – I recall my father-in-law who lived in Orkney coming home and telling us the golf course was under water and they were putting carp on the greens J
The Sterkfontein Dam by contrast has a 93m high dam wall and has a surface area of only 70 sq kilometres. Built to capture water from the Lesotho Highlands and Tugela it does not rely on rainfall – but if it did it, would take 17 years of rainfall to fill.

The South African Weather Service is predicting an end to the drought. (They have been known to be wrong before J). The El Niño warming the Pacific Ocean leads to drought in the southern hemisphere has tailed off. Nasa predicts there is a 60% chance it will be followed by the wetter La Niña.

The numbers just don’t add up. Johannesburg Water says 40% of its water is used on lawns but there is hardly any mention of the 35% loss through leaks in the water pipes feeding the cities and from people using water and not paying for it. Further industrial consumption of water is huge. What about drinking water? One of books prescribed for 1st year university students of statistics is “How to Lie through Statistics”. It seems to apply here.
In Saudi Arabia, a desert country, has overcome water scarcity by making substantial investment in seawater desalination, water distribution as well as modern sewerage and wastewater treatment plants. 50% of the fresh water comes from desalination, 40% from mining of non-renewable groundwater and only 10% from surface water in the mountains.

What should Koi Keepers Do?


We have to provide a healthy environment for our koi. Koi keepers recirculate the pond water. Good filtration and water changes are the way to go – just as you have been doing for years.
If you have a bore hole you do not have a problem and these measures need not apply to you.

Firstly – make sure there are no leaks in the pond. Leaks can occur anywhere, in the filter chambers, in the piping, in waterfalls and streams, hair line cracks in the walls. Any possible area where water can be lost should be repaired.
If a single drop of water leaks out of your pond each second you will lose about 3.5 - 4 millilitres of water each minute. This is 240 ml per hour or 5.7 litres of water each and every day of the year. That's over 2000 litres a year!
Secondly we need to consider all the elements that contribute to water quality degenerating. Water is a complex eco-system consisting of a host of water quality parameters. Fortunately only temperature, suspended solids, oxygen, pH, ammonia, nitrite, nitrate, carbon dioxide and alkalinity play an important role.

Each water quality parameter interacts with and influences the others. When you start changing one, another will be affected. For example: low dissolved oxygen in the water will mean high carbon di-oxide. Another example: At low pH (below 7) most of the ammonia in a pond is in a non-toxic ionized form. Simply adding baking soda to raise the pH will raise the unionized ammonia to toxic levels. Increasing the pH level by 1 point from 6.5 to 7.5 increases the unionized ammonia concentration by a factor of 10 !  A 1 point increase in pH = 10 times increase in the toxicity of ammonia. And this could easily kill your koi.

Oxygen, ammonia, nitrite, nitrate and carbon dioxide will be taken care of with your biofiltration + circulation at all times. pH and alkalinity should be stable. But how about solids? And what effect do solids have on water quality?
Prof. Timmons in his book Recirculating Aquaculture states that suspended solids adversely impact all aspects of a recirculating aquaculture system, so the first objective of any recirculating treatment scheme is the removal of solid wastes. Large amounts of suspended solids will have an adverse effect on out koi.

There are massive amounts of solids generated in all ponds. Suspended organic matter in water includes remains of organisms in various stages of decay and living phytoplankton, zooplankton, fungi and bacteria. One of the main ones is algae. We have enormous amounts of sunlight in South Africa. Sunlight encourages algal blooms.

Dissolved substances found in pond water include compounds such as sugars, fatty acids, humic acids, tannins, vitamins, amino acids, proteins and urea. These can be seen as Dissolved Organic Compounds (DOC) or scum on the surface.
In ideal circumstances these are reduced by frequent short flushes of the filter chambers.

Getting rid of the organic material on a regular basis will go a long way towards keeping our ponds healthy and keeping disease away.

One of first measures for water saving is to control organic material build-up – usually in the filtration system and this will prolong water changes and filter flushes.
Suspended solids are generated from faeces, biofloc (dead or living bacteria), uneaten food, algae and atmospheric pollution.

Algae, dead and alive make up a huge amount of the organic pollutants found in our ponds. Organic pollutants, such as algae, contribute to oxygen depletion and ammonia increase. The rapid and complete removal of solids must be done or the other process in our ponds will fail.

As koi keepers we re-cycle the water of our ponds, this in itself is a major contribution to water conservation. But we have to clean filters – any filter – and this uses water. We need to effect water changes because the pond water gradually degrades in quality and this has an impact on the health of our koi.

You can save on a lot of solid production by reducing feeding - if you over feed or have a very high stocking density with a lot of food been introduced into the pond.

Keeping the algae under control will also help reduce the back-wash frequency and time. Don’t overdo it as many algae killers are plants poisons. There are natural algae inhibitors such as Barley Straw. Many ponds have reached a biological balance and do not have an algae problem. But algal production in the pond water is seasonal and they can reproduce themselves many times an hour. So the frequency of flushing filters varies from season to season.
Many koi keepers are flushing filters onto the garden or doing water changes on to the garden then filling the pond with fresh water. In this way no water is wasted and the pond gets regular fresh water changes.
Further, in California they are using chemicals to rejuvenate the pond water in times of drought when ponds are hardly ever back-washed.

In Balito, KZN the two year water restrictions have just been lifted. Near-by Durban still has water restrictions in place.

Koi keepers in Balito managed to purchase small quantities of recycled water to top up ponds and swimming pools. Gardens were never watered but survived quite well. Their lawns took the brunt of the lack of water.
I spoke to Mike Harvey and this is a quote on water restrictions:

“Amazingly without flushing filters the system coped – I have streams with plants in and that coped with the nitrates, freshwater shrimps and tadpoles managed to keep a lot of the waste under control and I did in later times start to use BioActive Plus just as a precaution.”

SAKKS uses a specific chemical to control ammonia in the Koi Show vat – why not use chemicals to rejuvenate pond water to save usage in time of water restrictions?
In researching this article I came across several references to using Potassium Permanganate to rejuvenate drinking water. Looking further into this it appears that low levels of Potassium Permanganate, used regularly for several weeks will rejuvenate pond water and not damage the bio-filer. The secret is low doses. Nowhere near the dose used to control parasites.

Alternatively one can use some products that help control impurities and organic solids in the pond and one such product is BioActive Plus.
I quote from the packet – “BioActivePlus is a high potency (>1 x 108 CFU/g) natural product that has been developed using propriety natural bacteria specifically for the aquaculture market.
BioActivePlus assists with the bioremediation of recirculated aquaculture systems by boosting the nitrification cycle and reducing the concentration of ammonia (NH3), nitrite (NO2) nitrate (NO3), COD and phosphate (PO43-).

System quality is further enhanced by the reduction of solids, organic waste and algae bloom proliferation.
Using a process called “Competitive Exclusion”, the beneficial bacteria in BioActivePlus outcompetes disease causing pathogens, thereby reducing the chances of sickness and disease. This allows the fishes own immune system to function optimally due to the reduced pathogen load in the aquaculture system.”

A summary of water saving measures for koi keepers.



Fresh Water Usage

Seal all leaks.

Keep water changes to a minimum.

Flush filters on to the Garden.

Add fresh water to the pond after flushing water on to the garden.

Chemically purify the existing pond water to reduce the frequency of water changes.

If you have a good working filtration system you may not need to do chemical treatments of the pond water.

Faeces and Uneaten Food

Reduce Feeding


Biofloc must remove from your system. In times of drought increased length of time between backwashes will allow biofloc to develop.

If you have a mature system and it is large enough it will surprise with how it will cope with longer intervals between backwashing.

Organics / solids

If these can be reduced, the time between filter cleaning and topping up the pond will increase thus saving water.

One way to do that is by using Potassium Permanganate to rejuvenate the pond water (PP).

PP is a strong oxidizer and it will burn off DOCs (an undesirable component that tends to build up in ponds and filters) plus pheromones and organics.

PP is used in drinking water purification.

The dose used to rejuvenate water is much lower than the dose to kill parasites.

There is no need to by-pass biological filters.

It is estimated that 1 low-level dose of PP is the equivalent to a 20% water change.

Knowing the volume of the pond very accurately becomes less important at low dosages.

Use of Potassium Permanganate to purify Pond Water.

The usage of PP – 1 level teaspoon per 10,000 litres. (5 grams / 10,000L).

If the water dose not stay pink/purple for about 2 hours repeat dosage on same day.

If the water stays pink for longer it means the water is clean.

Repeat single dose each week at 1 level teaspoon per 10,000 L for 4 weeks – 6 weeks.

It is most important to keep water well aerated.

After this procedure return to normal filter and pond maintenance.


No other medication / chemical should be used before treatment.

Chemicals like Sodium Thiosulphate will neutralize PP immediately.

Other methods of purifying Pond Water

Ozone treatments

Activated charcoal filters

Editors Note: The Chris on Koi stories have been researched from scientific material and drawn from personal experience. Koi keepers needing further information or assistance can contact Chris Neaves at 082 495 6217.

Last Updated on Wednesday, 02 November 2016 20:44