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)

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.

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Aug 08, 2017
Pond Fish Density
by: Grant

Hi Lorraine

Your pond filter gph is excellent, minimum turnover for a pond is once every 2 hours.
A slightly acidic test result can indicate water that hasn't been freshened for a while. PH tends to lower over time even though the water appears clean with no ammonia present.
Purchase an inexpensive test kit and check the water regularly as pond water conditions change over time because of the seasons.
Check the pH of your water source as that is your starting point. If it is slightly acidic your pond water is fine.
For a 1000 gallon pond with active fish that can grow to a maximum body length of 8 inches, 15 Comets/Shubunkins would need 450 gallons.
Double that for seasonal changes (summer heat), and your fish density is about right without the babies.
This is assuming you are running the filter 24/7.

Aug 05, 2017
by: Lorraine

Thanks for the advice. Built pond 3/17. The pond does have a filter system with 4000 gph pump but due to brook up hill, it probably changes out 2Xhour. There are three water falls. I had water tested and no Ammonia. Ph was slightly acidic. Should that be a concern? If so, what is best way to correct?
One other question... what is max number of fish (shubunkin and comet) you would have? I have 15 fish but now there are approximately 10 babies.
Love my water garden and the fish! Wonderful hobby!

Jul 19, 2017
Water Quality in Small Ponds
by: Anonymous

Watch you pond for bubbles at the surface. If you have bubbles that stay on the surface, you've got a water quality problem or you're on the way to problems. The testing is also important, but most people walk past their pond several times a day and can glance for surface bubbles. I also strongly suggest some type of filtration or at least aeration for goldfish. they are beautiful and low maintenance, but they are extremely messy. I've been fooling with goldfish for about sixty years and love doing it, but they do require some TLC. If your pond is where a very small runoff isn't a problem, you can have a extremely slow dribble of water from a hose or an ornamental fixture continuously entering the pond. A word of caution here, make sure your children or the neighborhood children aren't able to adjust the flow. All you need is a little water spilling from the pond. This means you are replacing the water that evaporates plus a small amount of the pond water with fresh water.

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