Water Changes in Pond Fish

by Lorraine
(Fort Valley GA)

I keep reading you should change out water but is that needed in a outdoor pond? (1000 gal)

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Grant's Reply


Hi Lorraine

This is a very good question as the logistics of water changes or a complete pond clean out can be daunting.

Unfortunately, a pond is only a larger version of an aquarium, so the same rules apply.

Ponds are harder to manage because they are subject to larger environmental changes and in some cases wind blown debris which aquariums are not.

There are several ways to minimize water changes or pond maintenance.

The most important factor is Goldfish numbers. The smaller the number the less maintenance is required.

Depending on location, rain can freshen the water, but when it is most needed during hot weather, that is when there is usually the least rain.

Filtration as an Option

A 1000 gallon pond is quite a large pond to manage.

You don't mention whether you are running filtration, but the way I would approach maintaining a pond of this size would be to run a filter with a UV clarifier.

This takes care of processing waste, and stopping the inevitable algal bloom caused by all the nitrates in the water from the filtration.

A filter helps avoid having to do a complete clean out as all waste is being processed continuously.

You may need to siphon off the bottom occasionally if you see a build up of detritus.

I would test the water weekly to ensure nitrates are below 30 ppm (parts per million) and the pH is around 7.0.

If they move outside these parameters, the only solution is a partial water change.

If you find the pond exceeding these parameters quickly, say within a week of a partial water change, then there are too many fish in the pond, they are being fed too heavily, there is too much organic waste getting into the pond or a combination of all three.

If you don't want to install filtration, the same testing rules will apply, but you will find fish numbers will need to be very low, and periodic clean outs will be required.