Avoid Changing Koi Pond Water if You Can

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Page Summary:  Changing pond water is a very bad idea unless you really really have to. If you have to change pond water then before you do pump as much as possible of the old pond water into a container and place the koi or goldfish in this holding area... make it as big as possible. Once the fish pond is ready to be refilled empty the old water and goldfish or koi into the pond. Then slowly over a few days add more water. This way the koi or goldfish are not subject to severe shock both in and out of the fish pond. Under no circumstanced feed fish before and after emptying the fish pond. If the only reason to empty the pond is to clear the bottom of accumulated debris then consider using a pond vacuum rather than emptying the pond. This will save you a lot of potential grief. In summary emptying a pond (even partially might be a bad idea). Having said this read on if you feel brave enough to start changing the pondwater.

Koi pond water change

Ponds and water gardens can give us a great deal of pleasure, particularly when they are stocked with koi or goldfish. But it is really important to make sure that you maintain the quality of the water in your pond or in any other water feature you choose to construct. From time to time this may involve a partial water change.

Maintain good quality water in your koi pond

The best way to maintain the quality of water in any fish pond is with a biofilter. This device will filter out pollutants constantly, ensuring that the water remains clear and healthy. It will take a while for the filter to mature, but once it does, there shouldn't be much that you have to do to keep the water clean, other than remove obvious debris, after a storm for instance.

You could also test the water regularly to make sure that ammonia and nitrates are not evident in the water, and to ensure that the pH remains within acceptable levels.

Apart from the basic quality of water, the hardness or softness of water is another factor to consider. There's not a lot we can do to change the water supplied to our homes, but it helps to be aware of the differences. For instance, so called "soft" water has a low mineral content. Soft water also tends to be acidic, which is a critical factor in the life of fish, especially koi, that are adversely affected by acidity.

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"Hard" water, on the other hand, has a high mineral content (usually with calcium and magnesium salts in it) and in fact we measure the hardness of water by the amount of calcium carbonate in the water. While typically soft water contains no more than 50 mg per litre of calcium carbonate (CaCO3) very hard water might contain more than 300 mg. We can add sodium carbonate to water to soften it, and calcium carbonate to harden it. The addition of CaCO3 will also ensure that the water is less acidic.

Reasons for having to change the water in our fish ponds

While a well balanced pond stocked with koi or goldfish will usually sustain itself, maintaining a reasonably good quality of water, both natural and manmade factors can negatively affect the water. For instance, sudden temperature swings – particularly upward swings – can have an alarming impact. If it suddenly gets very hot, algae can bloom and make the water cloudy. If the fish spawn spontaneously, the pond could quickly become overstocked which would eventually result in an excessive amount of excrement in the water, polluting it. If you overfeed your koi, or if the temperature drops suddenly and your fish don't eat as much as they normally do, then the quality of the water will deteriorate as the excess food disintegrates and rots.

If the water in your fish pond isn't balanced, and is either too alkaline, or more dangerously too acidic, then it's a good time to partially change the water. If there is ammonia or any evidence of toxicity, specifically nitrates, in the water, this is another good reason to partially change the water. Aim to keep the nitrate reading well below 25 ppm all the time.

What a partial water change entails

Since fish (particularly koi) will become stressed if you change their environment radically, it is best to carry out minimal water changes relatively often, rather than fewer partial changes that involve draining a large amount of water from the pond. A good rule of thumb is to limit the amount of water you remove and replace to 20 per cent of the total volume of water in the pond. Also take care not to alter the temperature of the water radically. Adding icy cold water to tepid pond water in the height of summer will surely shock your fish.

To remove the water, all you have to do is vacuum or discharge the primary filter chamber or bottom drain.

Of course it is sensible to test the water you are using to replenish your koi pond water. If there are contaminants in the water, or the nitrate levels are unacceptably high, you will need to take steps to rectify this, by possibly using a water purifier, or adding chemicals to the water – a tap water conditioner for example. A good quality conditioner will get rid of damaging chlorine, metallic content and various other potentially damaging contaminants. Just be sure that you establish the volume of water you are treating, and always follow the manufacturer's instructions carefully. Once you have completed the partial water change, recheck the nitrate levels again.


Don't stress over pond pH and Testing Koi Pond pH

Interpet Koi Pond Test Kit

I will make a few very important points here which should be taken very seriously by anyone contemplating measuring pH in a koi pond and then TAKING ACTION based upon the measured result from testing the koi pond's water. If you test do it reliably... Interpet lead this pond water testing field of the koi keeping hobby

  1. pH of koi pond water will vary depending on time of day measurement is taken and especially if plants are in the pond. This means if you take a pH at 9am it will not be the same as a pH taken at 6pm. This single piece of information therefore must never be the information relied upon to make fundamental decisions
  2. pH is notoriously difficult to measure even in a laboratory with sophisticated instruments let alone in a koipond or fish pond using a piece of litmus type paper or a vial with coloured scales on it.
  3. If you must measure pond pH and this is a great part of the hobby then take the pond pH at the same time every day and plot the result on a graph. So now what you're looking for is not a single pondwater result but rather a pH trend in the pond water that you can use to sensibly consider a pH strategy.
  4. Very high pH in a koi pond is a serious threat to the well being of koi when levels reach about 9.5 because at this pH level ammonia which is a natural metabolic product of the koi and its existence becomes extremely poisonous
  5. It would be extremely rare for a koi pond to reach dangerous pH levels but could well occur in koi ponds with serious algae problems

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