Why Has My Fish Pond Got Foam Floating On The Surface?

I have recently received a couple of emails from newsletter subscribers asking me why their pond appears to have foam floating on the pond surface.

I thought it might be a good idea to write an article about this so as to help anyone else who may have a pond with the same symptoms.

There isn't a single answer as to why foam forms but is down to one of several reasons which I've covered in this article. I've also pointed out what can be done to cure this or significantly reduce the symptoms.

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Dissolved organic compounds (carbon based compounds) released as a by product of Koi, goldfish and other aquatic pond life eating, breathing and generally existing in the pond will over a period of time increase.

Unlike ammonia and nitrite which is broken down by beneficial nitrifying bacteria (Nitrosomonas and Nitrobacter) these organic compounds are only removed by heterotrophic oxygen using bacteria. Often as a result of insufficient oxygen the bacteria are not completely able to break down the organic compounds.

In extreme cases the pond water will often become discoloured and rather unattractive in appearance.

Whilst the formation of foam bubbles often isn't particularly threatening to the health and well being of the pond inhabitants it is never the less a bit of an eye sore if left.

The secret to a healthy pond is to carry out frequent pond water testing using a suitable pond testing kit. Whilst the vast majority of pond keepers will test for ammonia, nitrite, pH as a matter of course there are other tests that should be carried out if you want to be in full control including alkalinity, chloride, dissolved oxygen, hardness, carbon dioxide, temperature.

An excellent Pond Test Kit that includes all these is the LaMotte Test Kit...

Likely Causes Of Pond Foam Forming...

Excess pond algae can often cause pond foam to form because this microscopic single celled plant life is often so abundant, despite using a UV clarifier to control its growth that the level of organic compounds released into the water is high.
The addition of pond chemicals, in particular water conditioners that contain vitamin complexes often cause pond foam to form. Some pond medications also cause foam to form on the water surface.
Agitation from a pond waterfall or venturi will often cause foam bubbles to form which will eventually burst after a short period of time (few minutes).
Excessive feeding of high protein Fish Food will rapidly cause other soluble compounds to leach into the water, resulting in the formation of foam. Always feed just enough floating pellet food and remove any uneaten after a few minutes.

How Do I Get Rid Of Pond Foam?

Frequent Water Changes - This will help to reduce the level of organic compounds present in the pond water and as a result should help to reduce the effect of foam forming. Adding less organic laden tap water should reduce the formation of bubbles. Please be aware that tap water contains chlorine however so you will need to treat the pond water using a chlorine removing product.
Vary The Fish Food - The most likely cause of increased organic compounds is as a result of feeding high protein diets. This encourages the build up of algae cells that feed on the nutrients, subsequently releasing proteins into the water. Try varying the diet a little with a diet that isn't quite as high in protein.
Install A Pond Skimmer Filter - This isn't fantastic however as the Pond Skimmer Filter merely removes the foam from the pond surface to the pond filter. It is then recycled back into the pond again. This will result in the bubbles continuing to form. It does however prevent debris from falling to the pond floor thereby reducing the opportunity for pond sludge to form.
Install A Pond Protein Skimmer - This is the best way to keep pond foam to a minimum. Borrowed from marine fish keeping, several pond models are available, and through the vigorous aeration or water movement encourage the formation of a protein-rich foam which is collected and then removed from the pond water.