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Why do I have foam on my pond? | Decorative Ponds & Water Gardens Q & A

Why do I have foam on my pond?

Q: Why do I have foam on my pond?

Dom – Bellingham, WA

A: Foamy pond? No, the neighborhood kid (hopefully!) hasn’t dumped dish soap into your water garden or fish pond. The bubbly white or gray stuff you’re seeing on your pond’s surface is actually being caused by high levels of organic material in your pond. It’s natural – but it indicates an out-of-balance problem in your pond.

Question Your Water Quality

Foam forms when excess organic material has accumulated in your water garden. This happens when too many fish are living in the pond, you’re overfeeding them, you have inadequate filtration or there’s runoff flowing into the water.

When this nutrient-laden water pours down your waterfall, the air and water collide, causing the proteins and other organics to be trapped inside bubbles rather than turning into ammonia and nitrites. That air-water collision is why the foam seems to form at the base of your waterfall.

Tips for Removing Foam

So how do you get rid of the white frothy stuff? You can remove the foam in several different ways:

1. Use a defoaming product: A temporary solution is to dissolve the foam with a fish- and plant-safe defoamer, like Pond Logic® Defoam™. You simply shake the can and pour its contents into the water. The foam will disappear in no time.

2. Do a partial water change: To reduce the overall amount of organic material in your pond, you should drain the pond halfway or so and add fresh water and the defoamer. This will remove some of the organic material, dilute what remains and prevent foam from forming.

3. Reduce your fish population: Too many fish will produce excess waste, which means more foam. Remember that the rule is to allow 1 inch of adult fish per square foot of surface area – so if you have too many koi or goldfish in your pond, you might want to think about finding new homes for some of your finned friends.

4. Feed the right amount: If you’re feeding your fish too much, the excess food adds to the extra organic material in your pond’s water. Only feed your fish an amount they’ll gobble down in a few minutes.

5. Beef up your filtration system: A more powerful filtration system will remove those excess organics, so if you really want to erase foam, think about going bigger with your filter.

If you do suspect the neighborhood kids have dumped soap into your pond, your fish could be in danger. Do a water 90 percent water change before chasing the perpetrators down.

Pond Talk: Do you notice whether foam forms more often during certain times of year?

Pond Logic® Defoam™ - Eliminate Unsightly Pond Foam

14 Responses

  1. Rather suddenly my 5000 gal and went got very foamy. This followed the water getting a bit cloudy (with algae). Have a great filter system designed for up to 10,000 gallons. Have conducted 3 ~20% volume each water changes in the last week. Pond has a built-in skimmer where I can repeatedly collect the greenish tinted foam. I cleaned the heck out of the smooth cement bottom yesterday and plan to conduct yet another partial change-out and backwash. Pond is equipped with 2 30″ UV lights and I’d just began applying Microbe-lift PBL. My filter had been plugging up slowing the circulation rate in the prior week or 2. I blasted the inside’s bottom with a high pressure hose. I suspect the seasonal change, dirt and organic compounds on the bottom (although not visibly a large amount) and perhaps the spawning comets, and my water blasting of the filter media requiring destabilization of the media’s bio action all compounded to this? Pond is not heavily stocked.
    Your thoughts and suggestions going forward would be appreciated.

    • Hi Craig – It sounds like you have a pretty good understanding of what’s going on in your pond. All of those factors could definitely contribute the change in water quality and thus the foamy water. A quick change in weather can also cause your pond to take a turn. Keeping the bottom of the pond free from as much of the loose organic debris will help. Do you have aquatic plants in the pond? Plants are also great at filtering and shading the water.

  2. We just had over 8 inches of rain. Could this be causing bubbles?

    • Hi Suzanne – The rain itself would not be causing the bubbles but the agitation in water that is already high in organic debris along with the water runoff that was carried into the pond would also contribute.

  3. Yes when we first start the waterfall in the spring foams this year really bad for some reason put the gel bacteria on pads can that cause it or is it just due to not filtering for the winter

    • Hi Toni – The gel should not cause the water to foam, this is most likely just due to the amount of organics in the water and that now being moved. As the filter gets re-established it should clear up. If you need some relief in the meantime you can use Defoam as a temporary solution.

  4. When I bypass the waterfall the water is dumped into the pond at the same height, but the foam goes away . This a new fall& pond only two months old. 1700 gal pond with 50 fish 12 lbs by weight all Koi. Has a filter system in the bottom of the pond & skimmer. 4600 gph pump with matching filter. What do you think?

    • Hi Arthur – That is quite a few large fish for a new pond of that size. The difference when you bypass the waterfall is the amount of splashing. The more agitation at the water’s surface the more the foam will form. I would suggest a partial water change and also the use of additional bacteria to breakdown organics if you aren’t using any already. Depending on the weather in your area Nature’s Defense is a good one for breaking down fish waste.

  5. My pond has admintantly been neglegted the past 2 years, but the fish have been swimming about happily with no deaths. We decided to add a bigger filter to our pond as it was wofully under filtered before and since then we have had froth. I am doing some water changes and hopping that once the filter builds up the good bacteria it rights itself.fingers crossed none of the fish die in the meantime

    • Hi Eileen – The foaming should definitely clear up over time as the excess nutrients are broken down. You can speed up the process by adding additional bacteria to the pond and filter. Good luck!

  6. Foamy small Waterfall. Healthy Pond Dispenser do you think it will help

    • Hi Rick – Adding beneficial bacteria to the pond will certainly help over time, just be sure it is dosed properly for your size pond. Foam is caused from excess organic material in the pond that is agitated by water movement such as a waterfall or fountain. You can use products like The Pond Guy® DeFoam™ to remove the foamy residue quickly. For long-term control a partial water change, along with the use of bacteria regularly dosed for your size pond, will help keep the organic debris levels under control.

  7. I have been away on holiday for one week my friend was feeding my fish when i came back i was told that my pond turned foamy and i lost 15 comet fish, Help.

    • Hi George – Sorry to hear about the loss of your fish.

      Foam is usually the result of too many nutrients in the pond. For short term foam reduction, you can use a foam remover product, like Defoam, and doing a 10-25% water change. Also check that your biological filtration isn’t clogged or receiving reduced water flow. For long term solutions, see the steps above: be careful that your fish population isn’t too large, not overfeeding fish, increasing biological filtration.

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