Your pond was looking great, but all of a sudden it looks like somebodies poured a bottle of washing up liquid into it, the surface of your pond is is covered in white froth and bubbles and it looks unsightly, but why did it happen.
There are two possibilities why you have foam in your pond, spawning and protein froth, the foam itself is not harmful to your fish, but it is a sign that something could be up with your pond.
If this white foam is constant and starts spreading across your pond you could have an underlying problem that could get serious if not treated, if it’s only in small amounts of foam at the bottom of waterfalls or from fountains it could be harmless and will disappear in time.
This is a common problem and usually appears at the bottom of waterfalls, around fountains or where the water returns to your pond from your filter system.
It’s caused by an excess of proteins in your pond water from dissolved organics compounds (DOC), when water and air from your waterfall/fountain hits your pond it makes bubbles, the proteins get trapped in these bubbles causing the foam effect, in simple terms it’s just air and water mixing together.
It happens when the organic material that’s produced from fish waste (poo) decaying plant material and uneaten food is broken down so small it gets dissolved into the water (DOC).
It often happens at the start of spring when your pond is getting established after the winter months, but you can have foam at other times of the year, the main reason you could have a frothy pond at other times is because it’s either overstocked with fish, you’re overfeeding your fish or you have inadequate filtration and aeration.
What you can do in the short term:
You can remove the frothy water from your pond or use a de-foamer treatment to instantly remove the foam in your pond, but you should not use a de-foamer if you suspect your fish are spawning.
De-foamers will not treat the problem and should only be used as a quick fix to remove the foam that has already formed, the foam will come back if the problem is not dealt with.
What you should do in the long term:
If your pond is overstocked with fish try finding new homes for some of them, if you can’t get your fish population down to an acceptable level you will need to increase your filter to cope with the extra load.
Stop overfeeding your fish, only feed your fish what they can consume in a few minutes, a lot of these foods are high in protein, any food that is not eaten falls to the bottom of your pond and decays adding to the organic waste.
Increase your filtration or add an extra one even if your pond is not overstocked, if your filter is too small it will not filter your pond which could lead to a build up off organic waste which will upset the water balance in your pond, we always suggest you use a larger filter than recommended by the filter manufacturer.
Add plants that help to use up nitrates and increase or add aeration.
Do partial water changes, but always use a dechlorinator if using tap water to refill your pond.
Spawning fish can cause your pond to foam, there’s nothing you can do about it and the foam usually goes away in a day or two.
It’s caused by your fish thrashing and flailing around in the water, this causes any waste from the bottom of your pond to be stirred up causing the foam.
If your fish stops spawning and the foam goes away you dont have to do anything, but if the foam continues you will have to investigate further.
Test your water
We would suggest you check your water if you have a problem of any kind, this will give you good indications of the water quality and will often solve a problem.
You will be looking for spikes in nitrates, nitrites and ammonia when testing why your pond is foamy, this would indicate that your filter system is not able to filter the water properly and there is more waste in your water than it can cope with.
To sum up
The actual foam you see floating on the top of your pond is not harmful to your fish, but it could indicate a serious problem with the water quality in your pond.
If it’s not your fish spawning you need to investigate why your pond is has suddenly turned foamy.
There are ways you combat the problem, but you must act sooner rather than later, otherwise the water quality will start to affect your fishes health.