Rainwater To Top Off Your Pond??

While talking to some of our customers in the past we have found that there is a really big mistake being made in that some Koi keepers are using rainwater to top off their pond. Collecting rain water whether you use a collection barrel or utilize the roof as a source and piping it into the pond is not an uncommon occurrence. While it may sound like a good idea and you’re saving on water, you should never do this, and here’s why.


Rain water is acidic. What do we know about acidic water? It can alter your ponds pH balance and in high volumes this can cause a fatal pH crash. Keep in mind that the smaller your pond the more it will be affected by the rain. For example, ponds smaller than 1000 gallons will be affected more by the rain than a pond with 5000 gallons. Depending on the time of year, the length of time the rain and clouds have gathered and been polluted in the atmosphere can vary the acidity of the rain water. A high volume of rainfall will lessen the amount of control you have on your ponds pH balance. With this in mind, we feel it is best if you are using rainfall collection as a way to refill or top off your pond that you stop.


One idea we’ve heard discussed is collecting rainwater from rooftops into barrels or other storage containers. There are a lot of harmful bacteria that can build on your rooftop which would then come down into your collection barrels and would cause serious harm to your koi if you add this water to your pond. If your pond is covered and rainfall is not a problem, you still should not add rainwater instead of tap water ran through a filtration system to dechlorinate it.


This article is meant to give Koi enthusiasts information regarding using collected rainwater as a means to top off their pond, so please do not panic after reading this article. You could possibly have had pH level issues that led to problems in the past that was actually in response to heavy amounts of rainfall and at that time you did not know the reason for the changes. In an ideal pond, you should try to keep too much rainfall from entering your pond, a cover might come in handy for those rainy days. Remember to check your PH & KH levels regularly when you’ve had a lot of rain in your area. If your pH or KH levels are beginning to drop during those times the problem can be fixed by adding Sodium Bicarbonate(Baking Soda) to your pond.  Be sure to also read our article on Carbonate Hardness in your pond.


We hope that this article has helped to steer your clear from using rain water as an option to top off your pond. Remember if you have any questions or concerns please feel free to contact us, we are always happy to help!



  • Mar 22, 2018
  • Category: News
  • Comments: 0
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