Pond Water Changes




Changing part of the water in your pond is an essential and often overlooked aspect of pond maintenance.  Ensuring the health of our fish is critical and healthy water is the starting point to managing healthy immune systems.


Why Do Water Changes

There can be many reasons to perform water changes in your pond. 

Routine changes can be performed to reduce build up of minerals or toxins in the water.  For example a koi pond with few to no plants will always have a build up of nitrates in the water.  These nitrates can be removed by changing out some of the water periodically.  But pond water also collects other pollutants over time.  Routine changes will help keep the water as clean and pure as possible.

Special water changes may be done when a problem has arisen.  An ammonia spike requires action and dilution with partial water changes can be one of the best ways to help protect the health of our fish.  With other concerns of fish health, a water change can be a best first step as well.

IMPORTANT - Topping off the pond after evaporation is NOT the same as a water change.  The toxins are not being removed unless the water is.


How Often to Do Water Changes

The frequency of a water change depends on many factors, including the amount of water being changed and the reasons for the change.  Fish load and filtration will also be relevant.  A pond with too many fish or inadequate filtration will need that to be offset with more frequent water changes.  In general, it is wise to perform smaller water changes more frequently; instead of a 40% change once a month, consider a 10% change once a week.


How Much Water to Change

How much water to remove ties back into how often you are doing it.  Our routine changes may be 10-20% but if you are dealing with a dangerously high ammonia problem then you may want to do 50%.  


How to Perform a Water Change in the Pond

There are multiple ways to remove the pond water and what is best for your situation will depend on the existing setup.  You may have a drain valve that makes this process easier.  Others may choose to use the existing pump by disconnecting the piping that is run to the filter or waterfall.  Still others may use an entirely separate pump used only for water changes.  Or you may choose to simply use a pond vacuum or siphon hose.  But the result is the same, you are removing the water from the pond and sending it off to waste.  This water is heavy in nutrients so would be great to feed to an ornamental or edible garden. If possible, try to remove sediment from the pond bottom as you are removing water.  

Once the desired amount of water has been removed, it’s time to refill with fresh water.  As the water is being re-added to the pond it is best to run the hose at a moderate pace as to not change the water temperature too quickly.  If your water supply is municipal water it will have been treated with chlorine or chloramine, this must be removed.  When you get the hose running, add the dechlorinator product per the directions on the bottle.  If adding significant amounts of water it may work best to add half the dosage at the beginning and the rest about halfway through the process. Note that dechlorinator is best used to treat the volume of the whole pond, not just the amount of water being added.  

Even better is to remove the chlorine prior to the new water going into the pond.  This would involve filling barrels and pre-treating that water before adding it to the pond.  However, this is not practical for most of our ponds due to the sheer volume of water, but this drastically reduces the chance the chlorine or chloramine will harm fish or biological filters.
Make sure you DO NOT FORGET the hose is running.  You can use a hose timer, set a timer on your smartphone, tie a string on your finger, whatever it takes to make sure you remember to turn off the water.  

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