Have a couple of questions for the Newsletter I've been dying to ask.

A. Why are partial water changes recommended for ponds, especially since a fair amount evaporates and if you use a regulator, it's replaced a little at a time on a regular basis? Does the need for water changes depend on how well the pond is oxygenated, e.g., whether you have a waterfall and fountains operating?

B. How often should a pond be emptied, washed down, and refilled? If you have a stable pond, and clear water, does this throw your pond out of whack and create problems with restabilizing the pond?

Golly, great questions!

A) Water changes have different purposes in different seasons. In winter, when your filters are not functioning and your fish are mostly dormant, small, repeated water changes taken from the bottom of the pond removes the worst-quality water from the pond, taking with it the majority of the ammonia and dissolved organics the fish produce. Dissolved oxygen is not a major issue if you are using airstones set shallow to keep areas of your pond ice-free. Cold water loads and holds oxygen avidly.

In spring, as the filters start up and there is the inevitable lag between fish activity and biofilter capacity (especially with regard to nitrite levels), water changes are your only effective tool available to keep nitrite under control, and to dilute out algae blooms if you do not have a UV system in your pond.

Once your bioconverter is up and running and your fish are eating all they can hold, water changes are a source of fresh minerals and salts required by the fish for health and osmotic balance; they also provide carbonates (alkalinity) to maintain the buffering capacity (pH stability) of your pond, and help get rid of DOCs (dissolved organics) if you do not have a protein fractionator.

Evaporation does not accomplish any of these benefits. What evaporates off is pure water, leaving the dissolved impurities behind. The replacement water simply brings the concentration back to what it was, and then the fish add some more. (Uhh, are you sure that water loss is really evaporation? Could you have a leak somewhere?)

B) The best time to clean your pond is late summer or early fall, while the air and water are still warm. The goal is to remove as much organic debris (sludge, dirt, dead leaves, dead critters, Jimmy Hoffa, etc.) from the bottom and between the rocks as you can. Any retained grunge will continue to decompose during the winter, producing toxic gases and poisoning your fish. Bare liner ponds are easiest to clean.

Do not scrub or pressure wash your pond. The algae on the sides is good. You and your fish will need it for the winter, and the pressure washer will damage your liner. High-flow and low pressure does the best job. I reroute the output of my bottom drain through a feed pipe, and use the pond's own water as a rinse, first having drained and saved about 5/6ths of it into a big kiddie pool, along with the fish (grumpy) and the plants (confused).

When we replace the water, we either treat liberally with Amquel to counteract the chlorine/chloramine mix that is an eternal companion of Chicago water or run it through an activated charcoal cartridge hooked onto the hose. As long as you do not crash your filter with untreated chlorine, the fresh water adds buffering capacity and will *stabilize* your pond's condition.

Bob Passovoy
President
MPKS