General Question

gailcalled's avatar

What has your experience been with milfoil in a small pond? Have you tried grass carp?

Asked by gailcalled (54448points) August 21st, 2014

That’s the solution suggested to us by my neighbors, who own 90% of the pond. That was the suggestion made to them by the NYS Dept. of Environmental Conservation.
When used for weed control, they(fish) are sterile (triplod). I want only personal experiences please.

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24 Answers

gailcalled's avatar

@LuckyGuy:I was hoping you’d stop by while I beat spell-check into submission with “triplod,” which it hates.

syz's avatar

They are very effective (grass carp). Too effective, actually, and can completely strip a pond of vegetation (leaving no cover and food for other species).

My grandparents had a bow hunter come out to remove all but one for just that reason (they don’t typically take a hook).

The also get huge and look like freaky dinosaurs. (Very disquieting to swim with.)


LuckyGuy's avatar

I had them and likely still have the paperwork. I bought them from the state about 8 years ago. $12 each? My pond is 0.1 acres and I got 2. They were about 6 inches long when I put them in and they disappeared as soon as they hit the water. I figured I had just wasted my money. They did nothing for about 2 years. Then I noticed they were still in the pond and about 18” long, swimming in formation like a pair of submarines. They grew about a foot a year! After about 4 years they were scary.big.(about 4 ft long and about 9” wide) and were coming up to the edge of the pond to eat the weeds. They even ate cattails which they are not supposed to do. I was told when they get too big they should be “replaced”. Before I had to do the deed (which I dreaded) they disappeared. I figure a bear got them.
I have not replaced them, yet. The pond is still much better than it was.

gailcalled's avatar

Well, the die is cast here. Apparently there are now 5 carp in situ. At least, I have some information for future issues. No one is going to swim in this pond and I doubt whether my neighbor’s 6-year-old will be fishing.

Several brown bears have been spotted in the neighbor recently here also.

(4’ long and 9” wide?)

syz's avatar

^ Take a look at the photo in my link.

LuckyGuy's avatar

Yes. Mine were huge by the 4th or 5th year. The body was as big around as a dinner plate. I’m not kidding about being scary huge. I also have small mouth bass in the pond. They were never disturbed. Both species peacefully coexisted. The bass ate insects and the carp ate weeds.
And the bear ate the carp.

Five of them?! Nice pond! What did they tell your neighbor about “replacement”?

LuckyGuy's avatar

@syz That is quite a picture. I never saw mine out of the water but from my vantage point they did not appear to be that fat. They were more submarine-like. It was creepy to watch them pull on the grass along the edge of the pond.
I would not swim in the pond naked!

janbb's avatar

I’ve never had mille feuille in a small pond but I would eat it anywhere.

Buttonstc's avatar


Aren’t these the fish that are invading the Great Lakes. There is film of them launching themselves out of the water and colliding with people in speedboats and stuff.

They originated in China I believe.

Or am I thinkng of another huge species of Carp?

gailcalled's avatar

I wonder whether my resident great blue heron, who has eaten some peculiar things in his day, would consider the carp food.

LuckyGuy's avatar

@Buttonstc The invasive species is called Asian Carp a catch all term for a number of species. I see that it is the silver carp that jumps out of the water. The triploid grass carp are different. Triploid means they have 3 chromosomes, XXY, so supposedly they are sterile. These critters did not come over on the Ark. They are made in a lab by thermally shocking the eggs. I asked at the hatchery how they knew they we he pointed out a blue scar near the gill of each fish where they had blood drawn for testing. All that for $12! They lumber along in the water, slowly swimming in formation while eating vegetation.

Buttonstc's avatar


Thanks for the info. That was interesting

LuckyGuy's avatar

@Buttonstc I was kidding around with the guy at the hatchery when I asked how he knew they were XXY. I thought he was going to show me a fish with both a penis and a vagina. Instead he showed me the blue dot where they did the genetic blood testing! Incredible! How do they sell them for such a low price?
Apparently the state has determined it is better for the environment if people use their lab-made frankenfish rather than toxic chemicals to control pond weeds. Amazing.
If you get a chance to see one you will be thankful they cannot reproduce.

dappled_leaves's avatar

@LuckyGuy Grass carp is one species of Asian carp, and yes, they are invading the Great Lakes. It’s a problem, and introducing these species to ponds as a biological control for weeds is exacerbating that problem.

gailcalled's avatar

May my resident great blue heron have a hearty appetite. Lucky says that the heron wil enjoy the carp in the second year, when they are 12–18” long.

I have not yet had the nerve to open@syz’s linkā€¦the stuff of nightmares.

LuckyGuy's avatar

@dappled_leaves That is precisely why NYS DEC supplies the triploid grass carp – they are genetically modified to be incapable of reproduction – and they all have the blood test to prove it. You will not see a triploid grass carp on the Maury show being accused of being the baby daddy.
Even with that restriction you need a permit to put them in your pond, and the pond must meet certain criteria, no outlet to creeks, certain size, certain depth, etc. (I don’t remember them all. You can look on the DEC site. And, incredibly, someone for the DEC actually checks!
They hope to control invasive plant species that can move from pond to pond by birds or animals, without using chemicals. I can honestly say the TGC really cleaned up my pond without damaging any of my bass. But they sure were scary looking.

dappled_leaves's avatar

@LuckyGuy Yes, I understand what you wrote about triploidy, but the reality is that sex is a fluid thing in triploid individuals, and fish have a remarkable ability to influence their own sex chromosomes through hormones and environment. The papers on reproduction in triploid grass carp have a “well, we haven’t seen any direct evidence yet” feel about them. And papers on the proliferation of grass carp in the Great Lakes have a “gosh, they must be coming from somewhere. Maybe someone’s importing them illegally?” feel about them. One senses that it’s only a matter of time before the mechanism is found. Even in the 1980s, people were publishing on the likelihood of reproduction by XXY grass carp – the gonads can exist, whether they coincide in male and female XXY is a matter of probability. Given enough carp and enough time, it will happen. Particularly since human endeavours of this type are far from foolproof.

And fish have been moving from closed pond to closed pond forever! All it takes is for one of @gailcalled‘s herons to have a poor grip on his lunch.

CWOTUS's avatar

I don’t understand why people say they are “scary looking”. The one in @syz‘s link seems very… affectionate.

These are the jumpers. Not the same fish, thankfully.

If you have the time (44 minutes) and inclination, here are some big fishes.

gailcalled's avatar

If these carp grew up into syz’s images, we’d get a huge amount of publicity. My little bucolic and peaceful lane and pond with its wild yellow and blue irises, cattails, red-wings, herons, loosestrife, chicory, Queen Anne’s lace, elderberry, Joy Pye weed, thistle, blue vervain and milkweed is a small paradise, particularly at this time of year. What have we introduced into this mini Garden of Eden?

LuckyGuy's avatar

You wrote: “What have we introduced into this mini Garden of Eden?”
Five vegetation vacuum cleaners.

Let the heron take care of business.

(Or there’s this.)

gailcalled's avatar

@LuckyGuy: I noticed Milo busy ordering something online. I hope that it was one of these. I’m sure not getting close to the pond’s edge, armed or not.

LuckyGuy's avatar

They can eat up to 3x their body weight every day! Voracious! Just keep telling yourself: they are vegetarians; they are vegetarians; they are vegetarians…

That device is a wise purchase indeed. If Milo is a good shot you might save a lot of money. They can weigh up to 80 pounds. That’s a lot of fish!

Seriously, do you have other fish in the pond? You will be surprised to see how gentle and selective those bohemeths are. They don’t even eat insects.
Photograph the pond now and keep track every year. Note the changes. My cattails disappeared one year even though they are supposedly off limits.
In the long run (after the monsters are gone) you will be happy with the changes.

gailcalled's avatar

There had been some fish there 15 years ago when my neighbor stocked the pond for his young son to fish. The neighbor moved, the boy grew up and has his own children now so I have no idea what’s swimming around. And the heron has been breakfasting there every spring and summer.

I like the idea of starting a photographic record. I’ll get some pictures this week. The wild flowers are pretty there now. The loosestrife and wild yellow iris pseudacorus are spreading like mad. I had started to be concerned about them taking over and turning the pond into a wetlands. Maybe the carp will turn out to be good weeders. I guess that they are equal-opportunity gardeners?

Could one train the carp to eat ticks, mosquitoes and no-see-ems?

When a mature red-tailed hawk alit on my deck railing this morning and stayed for several minutes (to my delight) Milo didn’t even open his eyes. Will a giant swimming organic compost bin arouse his interest?

LuckyGuy's avatar

I put small mouth bass in my pond 20+ years ago to eat the mosquitoes, ticks and other water loving/breeding bugs. Supposedly they make a difference but I could not tell. There are still mosquitoes hanging around.
Per the DEC’s recommendation I tried trout first but they did not reproduce in my pond. They are finicky and prefer a certain amount of flowing water. I gave them a chance fora couple of years and then, again per DEC recommendation, put in 100 small mouth bass fingerlings. That was 20 years ago and they have been thriving. The GSOCB (giant swimming organic compost bin) did not affect them at all.
As for the red-tailed hawk getting a good meal that is not likely. The GSOCB move in slow formation near the bottom of the pond eating their greens. You will not see them for a year or two. They will only start coming to the surface when the bottom is cleaned up. That is the only time the red-tail can get them.
I will bet the heron gets them first.

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