Leeches are little critters that nobody wants to see or hear about. They look nasty, they smell odd, and they are unwelcome in most places. Now, with that being said, most leeches actually do not suck blood, especially not from the fish in your pond. However, there are actually some species of leeches that you might find in your pond that will affect your pond fish.

Today we are here to answer the question: how do leeches get into ponds? We also want to talk about some other pond and leech-related topics, too, like how to safely remove them from your pond. Let’s get right to it.

aquarium plant dividerHow Do Leeches Get Into Ponds?

To make something very clear, it is not actually that common to find leeches in a pond, at least not a small home pond with fish in it. It really depends on the climate, where you live, what kind of pond supplies you purchase, and where you purchase those pond supplies from. The fact of the matter is that there is only a small chance that you will encounter leaches in your pond, but there is still a chance.

Now, leeches don’t just spring up out of thin air and pop up in your pond out of nowhere. They do actually have to come from somewhere. Generally speaking, leeches will be introduced into a pond due to the things you put in the pond.

Leeches and leech eggs can be attached to the fish you buy, to plants, rocks, and within bags of substrate too. You will probably be able to spot a fully grown leech before it ever makes its way into your pond, as they are about 1 inch long.

However, the eggs of leeches are very small and hard to spot. If you have a couple of leech eggs on the plants, fish, or decorations you put in your pond, you are well on your way to having a leach infestation. Most leeches are found on the plants that you buy to put in your ponds, but this is not that bad because these kinds of leeches are usually not the kinds that will suck the blood of your fish.

gold carp pond
Image Credit: Zhukova Valentyna, Shutterstock

What Do Leeches Eat?

There is a bit of a misconception about what leeches eat. Yes, some species are well known for sucking blood, but those only make up a small fraction of all leech species. Many leeches are happy enough just eating pond scum. Various types of decaying organic matter will fall in your pond and sink to the bottom. Over time, this will rot and create a thick and slimy layer of pond sludge on the floor of the pond.

Many leeches love to live in that sludge, as well as to lay eggs in it, as it is usually quite warm and safe. At the same time, many leeches also feed directly off of this pond scum. However, many predatory types of leeches will actively hunt, kill, and eat other small invertebrates like slugs and snails. Some people prefer this kind of leech because they help to control worm, slug, and snail populations within ponds.

The other type of leech that you might find in your pond is, of course, the parasitic, blood-sucking type. They use a row of teeth to bite into the skin and attach themselves to the host. They use special chemicals to numb the pain and to make sure that the blood does not clot.

Say what you will, but these little guys are very skilled and efficient at what they do. Most blood-sucking leeches won’t be able to survive in outdoor ponds for very long, and some won’t even suck on your fish either. However, some species are dangerous to koi and goldfish.


Are Leeches Harmful To Fish?

Based on what we just talked about, no, most pond leeches are not harmful to fish. The types of leeches that eat pond scum or other invertebrates won’t ever bother your fish. Also, not all kinds of predatory parasitic leeches can use fish as their hosts. Either the blood does not taste good or they cannot bite their way through the scales of the fish. At any rate, there are only a couple of kinds of leeches that can actually do any real damage to your fish.

If you have koi or goldfish, the one type of leech that you need to look out for is the fish leech, also known as piscicola geometra. These are long, little leeches that can reach about 1 inch or 2.5 centimeters in length. They often come to your pond already attached to plants or fish. The full-grown fish leech can be hard to spot because it can attach itself pretty much anywhere to feed, which is problematic. After all, they often like to hide under fins and gills.

The leeches themselves might be a little unpleasant for your fish but are not actually deadly. However, they do cause stress and discomfort for your fish. They can be so stressful that they cause immune and behavioral problems. Also, the open wounds created by leeches allow other bacteria, viruses, and parasites access to the interior of your fish. Therefore, leeches can make your fish very sick indeed, even if it is indirect in nature.

leech curled on skin
Image Credit: Pixabay

How Do I Know If I Have Blood Sucking Pond Leeches?

Give the leeches bait to determine if they’re present. All you need to do is hang something like a piece of liver, or some other juicy meat, from a string and let it sit right at the water’s surface while still being submerged. If you have blood-sucking leeches it will not take long for them to make their way to the bait.

You can also just inspect the fish. If the leeches do not come to the meat, either they are not the kind that will feed on your fish or you don’t have any leeches at all. If you do find leeches, you can use the following methods to treat the problem and prevent them from coming back.

If you have blood-sucking pond leeches, you definitely want to take the right steps to remedy the situation, as they can multiply pretty fast and will cause damage to your fish.

aquarium plant dividerThe 4 Tips for Treating & Preventing A Pond Leech Problem

There are a few things that you can do to both prevent pond leeches from making their way into your pond and for getting rid of them, too. Let’s go over the best ways.

1. Inspect & Quarantine

The first thing that you should do to prevent leeches from making their way into your pond is to thoroughly inspect all fish, plants, and decorations. If you see any leeches or leech eggs, be sure to remove them right away.

On that same note, quarantining new fish and plants helps, too. If you quarantine your fish and plants, you can see if there are any leeches or even leeches that are ready to hatch from their eggs. Therefore, you can control the leech problem in a quarantine tank before they ever get to your pond.

We have covered a pond plant buyers guide here, which you might find helpful.

fish pond with frogbit leaves
Image Credit: toinkdunk, Shutterstock

2. Getting Rid of Bottom Sludge

One of the most effective ways of getting rid of all kinds of pond leeches is to remove the scum from the bottom of the pond. This will not work as well for the blood-sucking varieties, but it will still be of some assistance.

Leeches that feed on the scum rarely leave it. Therefore, you can suck them all up, along with the pond scum. You should get a good pond vacuum to do this, but you can also use a flat net to scrape the bottom of your pond.

Just be sure to be very thorough if you are using a net. A pond vacuum is the better choice because you can also suck up leeches and leech eggs. Even though blood-sucking leeches don’t eat pond scum, they still like to live among it, so reducing bottom scum is a big deal here. You can then add some kind of sludge-eating bacteria to the pond, which will help to remove any remaining scum from the bottom.

3. Add Leech Traps

Another thing that you can do to help get rid of leeches is to use leech traps. Now, you can make your own if you choose, but this is a bit of a pain. We would recommend buying pond leech traps if you can. Simply fill them with bait, put them in your pond, and check them daily.

If the traps keep filling up, you need to keep setting them to catch more leeches. Chopped liver seems to be the best bait to use for leeches, so we would definitely recommend giving it a try. If there are no leeches in the traps for 72 hours, you probably do not have any blood-sucking leeches left in the pond.

4. Remove Leeches from Fish

The other thing that you definitely need to do is to remove all leeches from your fish. Simply use a net to catch the fish and inspect them for leaches. Under the fins, gills, and stomach are the most common places to find leeches on fish.

Use tweezers to remove them. After you have done this, you should probably add some kind of anti-parasite and bacterial treatment to the water to prevent infections.

aquarium plant divider


When it comes to leeches on your fish or in your pond, most are harmless. The leeches that will feed on your fish do need to be handled, though. So, we would recommend following all of the above steps and tips to treat your pond for a blood-sucking leech infestation.

Featured Image Credit: Pixabay