How to Treat Egg Bound Fish

koi eggs surgery

Oh, goody! Another “disease” for our Fake Fish Diagnoses file. I recently received an email explaining how “egg binding” kills fish, and I figured it would be an excellent opportunity to set the record straight. Let’s learn all about what egg bound fish really mean.

Many hobbyists are unaware that koi, and many of their fish cousins, are constantly carrying eggs. In the warmer spring months, some of these eggs will mature and be released into the water column. The males will release their sperm at the same time to externally fertilize the eggs. If conditions aren’t right or there are no males to spawn with, females will resorb their mature eggs and wait until next year. This is a NORMAL process. If you open up a dead koi and see eggs, do not assume they died from “egg binding.”

Graphic pictures below!

The bilaterally symmetrical brown/red masses are immature ovaries in a large female koi.
Adult koi with mature ovaries

Sometimes, fish do not release their eggs. Why would they do this?

Environmental Causes of Egg Binding

Most likely the #1 cause of non-spawning is that your fishes’ environment isn’t suitable to spawning. This can be an individual fish issue or an entire group. If the water quality is poor, the male:female ratio is off, the pond is overcrowded or the fish aren’t receiving enough nutrients, the fishes’ brain will signal ‘don’t spawn.’ This is NORMAL. If your fish aren’t spawning, they know better than you.

Large koi females carrying eggs require extra nutrients and oxygen to keep their large egg mass alive. Adding in the aggressive spawning practice of male koi, it is rough on these females to reproduce. If you don’t have issues with spawning in your pond, this is not a bad thing! Too many ponds are overstocked due to “accidental” spawnings.

Never squeeze your fish to try and get them to release their eggs! This is extremely dangerous and can seriously hurt your fish!

Neoplasia (Cancer)

Koi with benign cysts or gonadal sarcomas will not spawn due to changes to their internal body structure. These fish will usually start to look lopsided in their bellies. Ultrasound will confirm the presence of a cyst, tumor or asymmetrical ovary. Cysts and gonadal sarcomas require veterinary care in order to resolve. DO NOT ATTEMPT SURGERY ON YOUR FISH.

The chances of your fishes’ eggs getting stuck inside them and causing the fish to die is very, very, very low. Just because your fish dies with eggs inside them does NOT mean the eggs caused them to die.

References (in case you think I like making all this up)

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5 thoughts on “How to Treat Egg Bound Fish”

  1. Donald McCormick

    Thank you so much for posting the information on your site regarding retention of eggs by koi. We had been concerned for one of our females who is in her second season of bulging. Possibly she will spawn this year (2021) and release. Comforting to have verified knowledge to rely on.

  2. Hello. I’ve had a number of fish over the years bloat up, curve, and die. This one is in the process. Wanted to include a pic hoot but doesn’t look like I can. Is there anything I can do? How can I send a photo to you.
    Thanks in advance.
    Frank

  3. I’ve got a goldfish which has grotesque swellings either side of it’s body, one side is slightly larger than the ther causing the fish to be slightly bent. This fish has been like this for at least a decade. It’s a lovely snowy white gold-fish with cherry red irregular spots. I cant be sure if it’s a male or female. I was hoping it was a female so she could pass on some her genes.
    So my question is can they carry on spawning and reproducing with these swellings or is that unlikely. Does this affect both males and females?
    I also have a Sunrise platy that I’ve had a for three years with the same condition, due to the colouration I know its a female. She appears perfectly healthy and has grown from a tiny little fish with the swellings to a very large platy with the swellings, also appearing to be perfectly healthy.
    What could be the issue, obviously it’s begnine or they would be dead already. I can’t be sure either of these fish are reproducing as I’ve never seen this happen a my fish spawn and give birth early in the morning or at dusk, the platies in secrete parts of their ponds in thick weed.

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