(818) 541-9944

19 June 2019


So Cal Ponds, Inc. logo on a white background
So Cal Ponds Inc.
19 June 2019 

A healthy pond is mostly bubble free. Bubble or foam formation on the surface of a pond is usually caused by dissolved organic buildup. This organic build up can occur for a variety of reasons. Including over feeding, heavy fish load, or poor filtration. But at this time of the year when we get calls from pond-owners complaining of a ton of bubbles or foam appearing on the surface of their pond, we know that the cause is most likely that their fish are spawning! In addition to the bubbles/foam, at this time of year, we may also hear the following complaints:

“My fish look like they’re fighting a lot!” 

“My pond has a stink!”

At this point, we would just give the pond owner a congratulations, because their fish are definitely spawning.

If suddenly, over a one- or two-day period, you get a lot of bubbles on your pond surface it may be that your fish are spawning. Look carefully at the sides of the pond. If they have spawned you will probably see hundreds if not thousands of very small eggs, about the size of the head of a pin, attached to the sides of the pond. If this is the case you will need to check the pond’s water quality over the next two weeks carefully (See test kits for koi ponds). When larger koi spawn, they release a huge amount of organics into the pond and filter system. Most filter’s bacteria is not prepared to cope with this extra load. You may get a spike in the ammonia and nitrite levels. You would do well to clean your filter as soon as you can in order to remove as much of this organic load as possible. If you are hoping to get some new koi from this spawn, you will more than likely have enough eggs in the pond to have some survivors. If you don’t clean your filter, your water quality may degrade to the point of endangering all of your koi.

Want clear water ALL the time? Your filter may not be up to the task! Consider upgrading your filter system. You may also need water treatments!

Most pond owners are pretty cognizant of the changes in conditions and “seasons” that affect our ponds. One of those “seasons” in our ponds, is spawning season; which typically occurs during May through June. Of course, sometimes a bit earlier or a bit later. Some last a bit longer than others, depending on where you live. And the “rules” of spawning get broken all the time when sudden condition changes occur that may trigger our fish into spawning mode out of season.


If you are not familiar with what to look for, so you can witness a koi spawning, there are some easy to recognize signs any pond owner can see.


We all know that our koi and goldfish get along very nicely, without aggression or competitiveness toward each other. This type of behavior makes up the vast majority of behavior we expect to see with our fish. Then one day spawning season hits and our fish are at each other’s throats, or at least chasing each other’s tails. The pond is full of fast, aggressive and frantic activity. The fish are chasing each other around and around, jumping clear out of the water at times, and jamming themselves into skimmer boxes, there is frantic group activity along the shoreline rockwork and plantings.


We also have pretty consistent water quality conditions with nice clear water, and a clean pond surface just about all year. Then spawning season comes around and we see that our water quality is different. It has gotten very murky, it seems to have a slick surface quality, and the surface of the pond is also very foamy and getting foamier. The skimmer box is packed with foam and gives out a very fishy smell when you open it. What the what!!!


Our pond’s conditions change quickly, drastically, and it isn’t all that pretty but don’t panic. Its nature and the will to survive. Don’t try to “treat” the water to get your normal day to day conditions right back in your pond. Step away from the de-foaming agent you are about to dump in your pond! Try to let your pond go through the entire spawning without interference. Let your filters take care of the water quality, let them do their jobs, it may not happen overnight; but they’ll do it. Your water quality will return to normal daily conditions, of course assuming you have proper filtration.

The fish behavior we witnessed with all that aggression and chasing will soon return back to its normal day to day slow dance of color within your peaceful pond. But koi are koi, and they are going to spawn how they see fit, and there is nothing we can do to change it. Don’t be too frightened to see the males beat the females pretty badly! The aggressive behavior is definitely stressful, sometimes deadly, to the females and you will see they get pretty beat up with torn fins and all. However, they too will typically recuperate with a little time, and return to normal day to day activity in the pond. The female koi may not talk to the male koi for a while, but just give them some time.

The stinky water will dissipate as well, and your pond will go back to (hopefully) it’s odor free state of being. If any smell lingers then carbon will do the trick to remove foul odors.

After the spawning is over, take a good look at your fish to see how they’re doing. Take measures if necessary. Make sure that they are being properly aerated, especially in very foamy conditions. A good pond aerator is always good to have on hand! After they have calmed down give a good rinse to filter pads they will be pretty nasty.

Just a few weeks you will likely start seeing darting little koi and goldfish fry around the edges of your pond; swimming in and out of the rockwork and plants where they will grow out until they are real deal baby fish. A short few months later, colorful little koi will be milling in with the bigger koi trying to get in on some of those delicious pellets being served up; and it will make you happy.

So, that is why we give our clients a “congratulations” when they thought that their pond had gone completely off the deep end!


So-Cal Ponds is here to help.


10164 Tujunga Canyon Blvd. Tujunga, CA 91042

(818) 541-9944

Mon-Fri: 8:00 AM - 5:00 PM

CA C27# 991368

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