Treatment for roundworms in a Koi pond

[Mark Helm]

Hello. Please, I need advice concerning roundworms, treatment, etc. I did search the forum, and found no info for this issue. I have a Koi pond, about 1000 gallons, with 4 good sized Koi. I have an 80 gallon filter pump with 3 large fiber mats, each 3 inches thick. I clean them 1 to 1.5 months. Water quality has been fine. I have a large pump, and run it each night for about 8 hours. I use a bubbler too. I use pond plants In the summer from a reputable source for shade and water health. I live in Georgia, USA. It is hot here! I have been operating the pond for a little more than 3 years now. So far, all has been fine. Right now, the Koi seem to be healthy. They are eating, too.

I noticed the worms while cleaning the filters. This was a first in 3 years. The worms are dark brown, 1 to 1.5 inches long, pointed on each end, and use a sucker (it appears) to grip and pull themselves along hard surfaces. They wriggle through water and swim somewhat as well. Using the web, I have identified these as nematodes (roundworms). This is my identification. No professional assessment as of yet.

Has anyone had this problem? Does anyone know if these are truly harmful to my Koi? I assume yes. There are 2 treatments that I see; fenbendazole (in food), and levamisole (in water).

I‘d like to treat the entire pond, fish and all with levamisole. Am I on the right track here? If so, does anyone know where to purchase? All that I have found online is for aquariums. At their prices it would cost $1,000 plus to treat my pond. Also, is it possible to calculate the proper dosage for my pond, using an appropriate dosage extracted from levamisole for mammals, which is readily available? My research tells me that it is nearly impossible to over dose fish. Thank you all in advance.

 

[Laaf]

It seems more likely you are seeing some kind of insect larvae that do not need treatment. Can you post pics of the "worms" you are seeing with something for a size reference? Do your fish seem healthy?

 

[j.w]

and welcome @Mark Helm
I did not know fish could get round worms.

 

[Mark Helm]

It seems more likely you are seeing some kind of insect larvae that do not need treatment. Can you post pics of the "worms" you are seeing with something for a size reference? Do your fish seem healthy?

 

[Mark Helm]

Hello, and thank you. This worm is about an inch long, and stretches out to about an inch and a half to move. It grips with its mouth to pull itself along. It swims by wriggling. I looked these up, and a photo I found said, I quote, “nematode (roundworm).” The site showed gut infestations in dead Koi. I’m really shook that I may lose my Koi. They seem ok. I can’t see any worms in the water. The site said infected animal feces runoff or even birds with roundworms can contaminate a pond with roundworm.

 

[Mark Helm]

View attachment 133629and welcome @Mark Helm
I did not know fish could get round worms.

 

[Mark Helm]

Hi! Nice to be here. Thank you for the kind welcome. I guess fish can get roundworms, among other worms. I have been reading a lot about it. Sure don’t want to lose my Koi! Never had them in there before.

 

[Laaf]

Might it be a leech? I am having trouble finding pics of roundworms online that look like that. I am not a fish expert. Just trying to learn. I would only treat if I was positive of the ID of the creature due to potential harms from the treatment.

 

[mrsclem]

It does look like a leech and the way you describe it moving sounds right. I have seen several in my filters from time to time but they never seem to be a problem.

 

[cas]

Here is some info I found on leeches:

Leeches get into your pond from a number of sources, but they usually come from the introduction of new plants, fish or rocks.
Leeches found on fish should be picked off and skin swabbed with a disinfectant.
Sludge at the bottom of your pond provides an excellent breeding ground for leeches.
To make a ‘leech trap’ to get rid of leeches:
1. Poke holes in the sides of a plastic coffee can with a nail. Holes should be 1/8 to 1/4 inch in size. The nail holes should leave a sharp burr on the inside of the can (approximately 50 holes).
2. Put about 1/4 cup of raw meat in the can (ground beef, liver, chicken or turkey giblets are recommended).
3. Put the lid on the can and submerge it completely in your pond. A rock placed on top of the can will prevent it from falling over and will help prevent snapping turtles from tampering with it.
4. Check the trap a couple of times a week and remove the leeches. Keep the trap in the pond until you no longer catch any leeches.

 

[WaterGardener]

Welcome.

I think what you have are plant leeches. I have them in my pond. They do no harm to the fish so I've never worried about them. They eat organic matter and rotting material in the pond.

They aren't the blood sucking type that we are probably all familiar with. They are harmless.

 

[Lisak1]

Those are indeed leeches.

I did want to mention that at 1000 gallons, your pond is on the smaller side for four big koi. I know you said they are fine and have been fine for three years, but a very common theme here is "my fish/pond has been FINE for X number of years... why are my fish all dying now?" The reason is the fish continue to grow and the amount of waste they produce exceeds the ability of the filtration to keep pace, leading to an unhealthy situation that can literally reach a tipping point over night. You say your "water quality has been fine" - do you actually test your water?

Another question - why are you only running your pump at night? Is this the pump that feeds your filter? If so, it needs to run 24/7 or all the bacteria in your filter will die, rendering it useless for biological filtration. When you say you have an "80 gallon filter pump" is that the pump that feeds your filter? If so, at 80 gallons it's seriously undersized. With a 1000 gallon pond you should be using a 1500-2000 gph pump to turn the water over 1.5 - 2 times per hour.

Sorry - I know neither of these was your question, but I would hate to ignore the obvious and have you come back in a few months and be dealing with a tragic situation.

 

[Mmathis]

This short article was interesting — it mirrors what @cas said, above. One thing it didn’t mention (or did it and I missed it — senility setting in) is that most or all “worms” go through a life cycle where the actual ”worm“ itself isn’t terribly harmful to the fish if eaten. They require a host (such as) a snail that is eaten by the fish — take the snail out of the picture, and the parasite can’t develop to harm the fish. This is one reason I’m not a fan of foreign snails in my pond (it’s just me, though).

I looked for a life-cycle diagram, but since we’re not 100% what you have, I couldn’t pin it down. Think of it like mosquitoes (and yes, we have had people on here in the past who didn’t want their fish to eat mosquito larvae because they thought the larvae would develop inside the fish — though mosquitoes offer a different set of circumstances...).

Leech Control - Resources & Blog: Ponds, Seawalls, Fountains, & More

Information about Leech Control. Our resources on the site are here to offer additional information for you to explore. Explore our extensive library of resources on ponds, seawalls, fountains, and more!

pondplace.com

 

[JamieB]

Agree with what I’m reading above. Unless it is something you know is harming your fish, let it live. If it frees you out, pay a couple of local boys to catch and remove them. $5 should get at least one interested kid to put forth effort, add in some cookies and lemonaid, your set! However, your koi will be overwhelming the balence of the pond soon. You need a bigger pond, or less fish, and 24 hr filtration that moves the water volume 1 1/2-2 times an hour. If you do go bigger, consider a big filter, it works great to provide lots of space for benifical bacteria, and it cleans the water well.

 

[j.w]

Yep now that I see the photo it sure looks like a leech to me!