Pond Cleaning versus Changing Water

Pond Cleaning versus Changing Water

Posted on Apr 5th 2021
Author: Bill Hoffman

To clean or not to clean… that is the question.

Whereas many of us love to see a sparkling clean pond, as if it was brand new every spring, it is not always best to clean it out. Follow these guidelines to keep your water feature healthy and beautiful.


If you are a diligent ponder, you will likely have taken all the steps to shut down your pond carefully in the fall. This means you cut back your pond plants, cleaned your filters and put them away to dry out, pulled your pond pump and stored it in water somewhere it couldn’t freeze, kept your aerator going, installed a deicer, and covered your pond with a net. The good news is, all that hard work you did in the fall will save you time and energy in the spring!

Most often you will only need to scoop out a few rogue leaves that fell in, make sure your skimmer and falls box are clear of debris (and unfortunately dead animals sometimes), re-install your pump and filters and fire it up. On occasion you may experience a strong unpleasant odor at first flow. But not to worry, it will dissipate shortly after the fresh oxygen starts to circulate through the pond.


A Water Change Will Suffice:


Usually, cold water means clear water because all of the suspended particles settle to the bottom in the cold. But if you are noticing a cloud stir up as water begins to flow, even though you are able to see all the stone on the bottom, it may be time for a small water change. There are filter mats that will pull a lot of particles out of the water over time; but just a few bright sunny days could end up causing algae blooms and green water for weeks while you are waiting for your pond plants to come out of dormancy.

When doing a water change, it is best to draw the water off the bottom of your pond. This is where the majority of contaminants settle and ammonia levels from decomposing organic matter are higher. The closer your pond water temperature is to the temperature of the water coming from the faucet, the more of a water change you can do. Water temps coming out of your garden hose are around 53°F. If your pond water is within the range of 50°-56°F, you can get away with about a 50% water change if you deem it is necessary.

Always make sure you are adding a water conditioner to treat only the amount of new water you are adding. For example; if you have a 2,000-gallon pond and do a 50% water change, you only need to add enough water conditioner to treat 1,000 gallons.

This large of a water change is not always necessary - especially if the water temps are warmer. You want to be careful not to change water temps too quickly for your fish’s sake, so sometimes a 10 or 25% change is good enough.


Time to Clean it Out:


Life can get busy and sometimes time just gets away from you… Maybe you didn’t have time to cut back your aquatic plants in the fall…Maybe you forgot to put the beneficial water treatment in last summer…Maybe a hole was torn in the net and the pond filled up with leaves… Maybe it just hasn’t been cleaned in several years and the water lilies have jumped out of their pots and are taking over the bottom. Whatever the reason muck and sludge has built up. There comes a time when you just need to clean it out and start fresh.

The best time, by far, to do a full pond cleaning is in the spring or fall when pond water temperatures are close to the same as water temps coming from the faucet. This will put less strain on your fish as well as keeping the beneficial bacteria, that is growing in the pond, intact.


A Few Things to Remember in the Spring:


  • String algae is almost always a sure thing. It actually filters your water until pond plants come out of dormancy. Pull out what you can by hand but do not over-react with water treatments. It could cause more harm than good.
  • Spring is a stressful time for your koi and other pond fish. Temperature changes relate to many physical and immunity changes in your fish. Spring is a good time to use pond salt to aide with the adjustments they need to make. Add 1 cup per 100 gallons to reach 0.08-0.1% - if salt levels are starting at 0.
  • Toads will likely invade your pond to mate and lay their eggs. For a few short weeks it will seem they have taken over, but they should be gone quickly. 


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