Keeping fish population down

ageamdAugust 27, 2010

I have a small pond. About 1000 gallons. I put in 3 Shubunkins and 3 Comets in this past May. Now have over 25 fish of various size.

How do I keep the population down? Can I introduce another type of fish that will eat the eggs or fry? I don't want to harm the current fish.

By the way, anyone want some fish? I live in Virginia.

Thank you,


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horton(6 b Ontario.)

Age, this is an up dated copy of a post I submitted some time ago.

Birth control for fish.

This is a method of fish birth control you could use by having a few spawning mops in your pond.

You can make a few spawning mops by cutting a hank of wool [bought at the dollar store] at one end and tying a loop of wool around the other end to form a wool mop head.
Hang the wool mops in the pond, submerged just under the surface.
The female fish like the softness of the wool and spawn onto it readily.

Remove the spawning mops daily, dip them into boiling water and put them back into the pond.
You will have cooked and sterilized the roe and adult fish will eat it.

You could just leave the spawning mops in the pond and the adult fish will still eat the roe, but there will be lots of roe that will survive and turn into small fry, then into adult fish.

It is always a problem getting rid of unwanted fish.
Some people will take them and let them die over winter, then restock with free fish the next year. A terrible thing to do in my opinion!
I only give fish to people, whom I believe will look after them properly and not treat them as throw away items as soon as the cold weather comes.
I hope you can find someone responsible enough, to care for them, if you do end up with too many fish in your pond.

    Bookmark   August 27, 2010 at 9:01AM
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koijoyii(NE Ohio)

When I put in my second pond five years ago I started with two shubunkins and six koi. One of the shubunkins disappeared. The one remaining had dozens of babies which were mules (cross between koi and goldfish). After this happened I went fishing for a bluegill. Gil, the bluegill lived in my pond for the next four years and I had not a single fry. I lost Gil last winter and this year I had hundreds of baby koi. Thankfully, a few members of this forum and a pet store took the majority of them off my hands. I still have several that were too smart to swim into the minnow traps. Once again this spring I went fishing for bluegill. I know a lot of members on the forum frown on this, but it is the only way I know to avoid having fry. I didn't quarantine the bluegill and my fish were all fine until last winter. We had sub-zero temps and hurricane force winds early in the fall and it blew my net into the pond where it froze to the surface before I could get home from work and get it out. Unfortunately when some of the ice melted I found a lot of my fish dead on top of the net that was still frozen to the remaining ice. Gil was one of the casualties as well as a lot of the mules.


    Bookmark   August 27, 2010 at 9:59AM
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Horton...I will try the mop idea.
Jenny....I am not sure about Blue Gill in the pond.

I tried to give away the fish but no takes. One local pet store said that would, so I went by and check their place out. They had dying comets and shubunkins in their tanks so I decided not give them any fish.

Would a regular minnow or similar fish be able to keep the fry population down?

I have to do something soon or the pond is going to get out of balance and than everything is going to suffer.

Where is a Heron when you need one :)

    Bookmark   August 27, 2010 at 11:14AM
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I had my own population explosion three years ago due to a spawn. My solution was first to remove all the rocks from the pond except the coping stones around the edge. I discovered that even with spawning mops, some of the eggs will go between the rocks where they are well hidden and secure, and will hatch.

This year, whenever the fish spawned, I lowered the water level below the level of the coping stones, removed the few plants that I keep in the pond, and let the eggs on them dry out. Then after a day or so, I refilled the pond and let the fish eat the eggs. I had zero babies this year.

    Bookmark   August 27, 2010 at 11:57AM
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horton(6 b Ontario.)

Age, minnows are the rabbits of the pond, they produce more fry than any other fish I have.
But they love to eat mosquito larvae.

    Bookmark   August 27, 2010 at 5:04PM
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hardin(7 SE OK)

Horton, I will certainly attest to the fact that minnows are rabbits in water. I figured my albino catfish would eat them. No such luck.

So far, I haven't had any goldie or koi babies, but I'm sure it will happen someday. Will have to remember this post when it does. All good ideas.

    Bookmark   August 27, 2010 at 11:21PM
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I have 20 assorted goldfish varieties-shubunkins, sarassa comets, goldfish and wakins. I also have 2 butterfly koi who are now about 12" long each--second year in the pond. Last year I found and netted out about 10 goldfish babies and kept over the winter in a 10 gal tank. They went back in the pond this spring so that brings the goldfish count up to 30--all are under 8 inches long even though some are 7 years old--think it may be because they get moved indoors to a smaller habitat for the winter.

This year I've seen a few very small fry-about 1/2" long along the edges but none over that length. I think the koi have been eating them as soon as they hatch. I call the koi "Scoop" and "Shovel" as they are voracious eaters!
One thing I do is if notice signs of spawning--the foam or active chasing is not feed the fish for a couple of days. Some may thing this is cruel but it seems to keep the population down. I don't think my koi are old enough yet to spawn so I'll see what happens next year!

You might try advertising them in your local paper if the pet store doesn't want them. I gave some goldfish away last year to a friend who has a 4000 gal indoor tank--built into the wall of his basement. I'll probably have to find a home for my two koi by the end of next summer as they will probably be too big to overwinter indoors.

I don't think the fish will listen to you if you tell them they're not allowed to do the happy dance anymore.

    Bookmark   August 28, 2010 at 1:55AM
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sheepco(MN z4)

I removed all the submerged oxygenator plants from my pond and it seems to have helped. With less places for the fry to hide the adults seem to take care of the problem.


    Bookmark   August 28, 2010 at 8:04AM
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horton(6 b Ontario.)

Patti, said "Some may thing this is cruel but it seems to keep the population down", after intimating that her Koi eat the young fry.
There's nothing cruel about that at all in my book, I also do not feed the fish if I see they are flashing/spawning, in the hope they will keep the pond population down by eating the roe /fry.

I believe it is worse if you just let your pond become so over crowded that disease and viruses can break out and decimate the 'whole herd'.

Along with using the spawning mops, I net out as many of the surviving tiny fry as I can catch and cull them. I do not like doing that, but it has to be done, you cannot dump them into our lakes or rivers where they will take over from our native fish and the pet stores don't want them.They have feeder-fish coming out their ying-yangs!
With any type animal husbandry,you have to keep the population in check and in concert with their environment,or problems will certainly arise with the health and general welfare of our charges.

    Bookmark   August 28, 2010 at 1:34PM
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if you live near hillsville va i will take a few of your fish.. and i know a man would take all of them. i'm sure he would pay you for them.. just let me know. my email is

thanks a bunch

    Bookmark   August 28, 2010 at 9:18PM
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Thank you all for you suggestions. I will try to implement some of them.
I posted on Freecycle and so far have given away 25 fish. I guess I had more than 25 fish in my 1000 gallon pond. I think I am down to about 20. It is hard to count the number of fish, maybe I could train them to swim in a line.

Loriques, I am about 3 hours away from Hillsville. I know your area pretty well since I lived in Sylvatus for about 3 months. Love the Fideler's Covention in Galax and the Flea Market in Hillsville. I don't think you want to drive up to Charlottesville but if you do I will give you a few fish.

Thanks again everyone.

    Bookmark   August 30, 2010 at 8:41AM
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