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0When a pond's fish shift to spawning mode, all sorts of things start happening in a hurry -- in turn whipping new pond owners into a frenzy right alongside their fish.  At these times, Mike Gannon counsels restraint and helps novices recognize and follow what's happening.


  By Mike Gannon

Late in May in any given year, the phone calls and emails start flowing to our offices in New Jersey.  The basic message runs something like this:  “Hey, guys.  My fish are fighting and it looks like my kids’ bubble bath liquid may have fallen into the pond.  The water smells weird, too.”

Our response to these novices?  “Cool!  Your fish like your pond so much that they’re spawning and the water will soon be teeming with babies!  So congratulations:  It’s a fish!”

Often, this is only the beginning of what can be a weeks-long cluster of exchanges between us at Full Service Aquatics (Summit, N.J.) and our newer clients.  Naturally, we’re happy to know they’re paying attention and have noticed these dramatic changes in their watershapes – and even happier that they’re curious about what’s happening and want us to tell them if there’s anything they should be doing to encourage or discourage what they’re seeing.  

When they find out it’s spawning season rather than a system failure, they relax.  Most of them find it fascinating, too, as an unexpected but significant byproduct of their decision to become pond owners.  Best of all, their inquiries give us a golden opportunity to teach them another of the many things they’ll ultimately come to expect with their ponds – and help them get even more involved in the ecosystems that are establishing themselves in their backyards.


The timing of spawning season varies somewhat from region to region, but here in New Jersey it’s typically a mid-Spring phenomenon that can slide a bit in either direction depending on when winter finally releases its grip on the land, the pond ice has melted and the plants and fish have started getting active again.  

1At some point during May or June, the calls will come.  Some years, they all arrive in a short burst; in others, the spawning season spreads out over weeks.  We know from experience that it’s a process that defies generalizations and calendars.

The important thing we let our clients know is that the arrival of Spring brings many changes to these ecosystems that persuade the fish to enter into spawning mode.  It usually happens in May and/or June, but we’ve known it to start “out of season,” either early or late.  It’s nature’s own rhythm, we say, not the turning of a calendar page.

We continue these conversations by letting them know that this is an important event in the life cycle of a pond – and remind them that it’s something we mentioned when we turned these ponds over to them.  Clearly, there’s no substitute for actually going through the process to make our past instruction mean something:  We’re never surprised when something “out of the ordinary” happens and our clients’ minds get focused on an unanticipated need for our support.

Most important, we tell these folks not to be overly concerned:  Spawning is an entirely natural part of a pond’s lifecycle and wouldn’t be taking place if conditions didn’t allow and encourage it.  “So relax,” we say. “You’ve done things right and the fish are ready to take natural advantage of your attentive care for their home.”

Once that sinks in, we start telling them what’s going to be happening and let them know a few key signs that any observant pond owner will see.


A key part of the discussion has to do with the aggressiveness that often leads pond owners to contact us in the first place.  Koi and goldfish tend to get along very nicely together, seldom competing and generally giving each other ample room to maneuver.  But all that changes once a spawning cycle is triggered, and suddenly the fish seem to be at each other’s throats – or at least chasing after and nipping their pond mates’ fins and tails.

2Overnight, it seems, the pond is full of fast, aggressive, even frantic activity.  The fish will harass each other, pursue each other and get so energetic that they’ll jump up out of the water at times.  They’ll sometimes even beach themselves on shoreline rockwork or planting beds and will need some help; this is also a prime time for them to get trapped in skimmer boxes, so, we suggest, these are places to check regularly.

It’s not just the fish that change:  Water quality takes a crazy hit in spawning season, and the crystal clear water seen the rest of the year gives way to an unusual murkiness with a sort of an oil slick on the surface in places where the water isn’t covered by foam.  Skimmer boxes will get packed with foam – and there will be a strong, fishy odor, too.

It’s no wonder our clients get agitated when they see this happening for the first time:  It’s not that we didn’t alert them to the possibility, but even so, it’s an alarming thing to see. What they’re witnessing, we say, is an expression of the desire of these fish to reproduce.  So don’t mess with things:  Don’t add chemicals to clarify, defoam or otherwise manipulate the situation.  And don’t even bother testing the water, because there’s really nothing to be done beyond riding out the cycle.

3For the duration of the spawning season, we tell them, substandard water conditions represent the “new normal” and they should just step back and let things proceed without interference.  Their filters will keep doing their jobs, and so will the plants.  It may not happen overnight, but things will eventually return to normal:  The fish will calm down, the water will clear and these ponds will recover their former visual virtues – assuming, of course, that all of this hasn’t been caused by malfunctioning circulation systems!

Within a few days, the nasty behaviors will subside and the fish will once again resume the familiar slow dance of color within a peaceful pond.  But koi are koi, and they are going to spawn how they see fit:  There’s nothing we can do to change it even if it means we have to watch the males gang up on the females, sometimes with bloody or even deadly results.  The injured fish will usually recuperate, we say, and things will get back to normal.

The smells emanating from the water will loosen their grip, too, and will eventually settle back into an odor-free state of being.  And if they linger, adding some carbon to the filter will speed the return to normalcy.

We can usually tell how captivated these clients are by what’s happening when they jump at our suggestion to take photographs or even videos of what they’re seeing.  For those to whom that seems a tad voyeuristic, we suggest that they at least should know how to spot eggs around shoreline rocks and plants.

Koi and goldfish eggs are clear, round and about the size of a grain of coarse salt, and if they want to be truly avid about it, we advise our clients to collect some of the eggs into a small container rigged with an aerator so they can observe the process without risking a tumble into the water.  


Once the urge passes and the fish resume their calmer behaviors, we tell our clients, it’s finally time for them to take a close look at the big backyard picture and see what needs to be done with their ponds – and then take those appropriate steps as needed.

4Start, we tell them, by looking at the fish to see what condition they’re in.  If there are wounds that don’t seem to be healing, it might be a good idea to help things along with medications or even a little recovery-ensuring isolation.  Then look at the water:  If the foam doesn’t seem to be dissipating at a steady rate, it might be necessary to step up aeration, either by increasing the flow to a waterfall or by placing a supplementary aerator in the pond.  

Then there’s one nasty chore:  It’s time to pull out the filter pads and give them a thorough rinsing.

The bonus to cleaning things up soon after spawning season ends is that the return of crystal-clear water will make it easier for our clients to see the darting forms of baby koi and goldfish zipping around near the edges of the pond, where they can easily take cover in the rocks or plants as needed.  Then, within a few months, these colorful little fish will emerge from the shadows and join the larger fish in trying to get in on some of those delicious pellets our clients are distributing at mealtimes:  All is again as it should be, and everyone is happy!

The next year, panic will be a thing of the past.  Instead, it’ll be time for cigars and greeting the next generation of a thriving pond’s population.  As we told them when they called us a year ago, “Congratulations:  It’s a fish!”


Mike Gannon is owner and lead designer at Full Service Aquatics, a pond installation and service specialist based in Summit, N.J.  A certified Aquascape contractor, he may be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

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