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I top off my pond for evaporation, so why do I need to do water changes? | Decorative Ponds & Water Gardens Q & A

Q: I top off my pond for evaporation, so why do I need to do water changes?

Q: I top off my pond for evaporation, so why do I need to do water changes?

Joan – Bethesda, MD

A: Topping off your pond with fresh water isn’t quite the same thing as a water change. Think of it like the oil in your car: You may “top it off” when the lubricant gets low, but to keep your motor humming, you need to do a complete oil change every 3,000 miles or so to remove the dirty oil that’s full of sludge and combustion by-products.

It’s the same idea with the water in your pond.

Adding water every week or so to replenish any lost from evaporation is certainly important—but it does nothing to remove the sludge, or algae-feeding nutrients, in your pond. As the water evaporates, the gunk stays behind and concentrates. Your filter does a good job removing the pollutants, but unfortunately it’s not always enough.

So why do water changes?

  • Remove the buildup of nutrients, like nitrates and phosphates
  • Promote fish health, as their well-being is directly related to your water quality
  • Reduce algae blooms

To keep buildup under control, we recommend you change 10 percent of your water every week, or 20 percent of your water every two weeks. Many pond owners use a spare pump and hose to draw out the dirty water and send it down the drain. If you have a pressure filter, using its back flush feature is the perfect way to make the water change.

If your tap water has chlorine or other heavy metals, don’t forget to make it safe with Pond Logic® Water Conditioner. It removes chlorine, destroys chloramines and detoxifies heavy metals. One ounce treats 500 gallons.

In addition, make sure you add some beneficial bacteria to the mix, like Pond Logic® Nature’s Defense® or LiquidClear™, because when you change the water, some good stuff goes out with the bad! Both products contain microorganisms that instantly activate once they hit the water, multiplying every 20 to 40 minutes as they digest organics in your pond.

Make water changes a regular part of your pond-maintenance routine.

Pond Talk: What water-change routine has worked well in your water garden or koi pond?

Neutralize Harmful Water Contaminates - Pond Logic(r) Water Conditioner

7 Responses

  1. We have two 100g Rubbermaid tanks with cut up floor scrubber pads as Bio-filters. I flush the tanks via the bottom side drains while agitating the filter pads. The drainage is directed to our vegetable garden and flower beds. Since we use no chemicals in our pond we believe this to be a safe form of Aquaponics.

  2. I have actually heard just the opposite. Do not make water changes because it upsets the bacterial and algae balance in the pond and contributes to a green water problem. Now I don’t know what to believe. Guess there are two schools of thought on this issue! Since my pond water finally became crystal clear on its’ own this past week, I think I’ll leave well enough alone. All the rain we’ve had this year seems to have made the green water stay around longer than usual. Something in the rain must feed the algae that causes the green.

    • Hi Linda – Pond owning is a big experiment. We find that many issues stem from water quality. We’re not suggesting to do a complete water change, just enough (10-25%) to get some fresh water in the pond. After a full water change, your pond does need to cycle again.

  3. What type of secondary pump do u recommend for draining some water from the bottom of the pond in midsummer?

  4. I take a bucket and scoop up water from my 35 gallon pond/water garden and use it to water my plants and garden. Then I refill with the hose and add some aquarium water conditioner. My koi’s are doing good in there.

  5. I take a 10′ length of 4″ PVC and saw off the top half long enough to fit under my water fall. By putting this under my waterfall I don’t have to shut off my pump which makes my water exchanges very simple.The easier you can make it the more often you are likely to do this very important procedure.

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