How To Remove Leeches From Your Pond Without Chemicals

Shortly after my parents moved in to the house where I now live, they decided to dig a pond. They wanted it to be natural and encourage frogs and newts. My partner and I left some goldfish from the fair in the pond one weekend while they were away. They were delighted (so were the fish) and over the next year or two they were given ghost koi, shubunkins and some golden orfe. Frogs came to the lily pond and established themselves. The pond was kept fresh by a water pump, water soldiers, water snails and mum's meticulous care removing falling leaves and debris. The plants spread, the ghost koi kept the balance. Herons came and took some of the fish, but it was peaceful enough. Chemicals were never used. Then the remaining big fish died one by one and the last fairground goldfish, now huge, succombed the week they moved into sheltered accommodation. I saw a leech on his body, but assumed it was there due to his weakened state.

We redecorated, refurbished, moved in and saw the pump was hardly working. It was important to fix this as it is the main factor in caring for your fish. At this point the frog population was healthy too because it was before the big freeze. The week we moved in, we bought a pump with a water filter and UV light intending to restock. We bought six comets and two green tench to join the little brown carp-like wild fish that we believed were the result of crossbreeding and reverting between shubunkins, goldfish and ghost koi. We couldn't believe how clean the pond became within days. One of the comets died - again we saw a leech, but didn't realize at that point that fish were being attacked by leeches. We thought it was because it couldn't cope with the move.


Cute Cartoon Hedgehog Calendar 2012 by persimew


We were keen to restock our pond, so when the weather warmed up, we went back to purchase some ghost koi babies and some small shubunkins. There were fewer frogs due to the harsh winter, and we wanted to get things back the way they were.... little did we know what awaited the new fish. Within days we had to remove a comet for treatment - it had a leech attached. Then one of the baby ghost koi died. That was when alarm bells really rang - leeches on pond fish are no joke!

Hmmmm.... how to kill leeches in pond..... If you want to go down the chemical route it is complex and dangerous. It is also expensive to buy pond chemicals in the quantities needed. It involves replacing all plants, estimating exactly how much water the pond holds, mixing chemicals that could possibly harm the smaller fish - and destroying every living invertebrate in the pond. That was not something we were prepared to consider. So what is safe to use to kill leaches? I searched and searched until I found the idea of constructing a leech trap out of a coffee tin. Here coffee tins are not so easy to find, they tend to be metallic cardboard. Then I thought of fresh soup containers and the leech trap was born.

At present we are on our third trap and numbers are reducing. I was horrified at the number of leeches in the last trap.... How you dispose of them having caught them is another issue of course, but you need to remember that leeches are dangerous, but they are also living animals with a nervous system and should be disposed of humanely. Freezing them is one method, or release into a river system, if it is permitted, where larger fish may eat them.

Apart from being gross, what is a leech? A leech is a water worm, it belongs to the phylum Annelida, class Hirudinea. The blood sucking leech is a parasite to animals, birds, fish, frogs and mammals - including man. Infestation by leeches produces a condition known as Hirudiniasis. Not all leeches suck blood, some are carnivores and hunt insects and snails. However about 75% of known species of Leeches are blood sucking external parasites.

Leeches secrete Hirudin, a chemical produced in their mouth glands, which stops blood coagulating. Up to the middle of the 19th century bloodletting by leeches was a common treatment. Medicinal leeches are sterile, but wild leeches can produce infection and ulceration when satiated as they drop off.

Leeches enjoy slow moving streams, ponds, lakes and marshes, and can live on on moist vegetation in jungles and other humid environments.

Someone asked this question:

How do you treat a pond that is your drinking water and it has leeches in our pond?

This is a very real problem! Drinking leech infested water can lead to fatal illness. Leeches have been known to attach to the throat or mouth and suffocate the victim or cause internal haemmorhages. If your pond is your drinking water supply then you must treat it aggressively. Treat with chemicals, neutralize, drain, remove and destroy all plantlife and allow the pond to dry out completely for several weeks.

This will basically destroy your pond wildlife, and you maybe don't want to be so destructive, so you are faced with two alternatives, chlorinate pond water with water treatment tablets from a camping store and then thoroughly boil it before use or find an alternative drinking water supply. Purchase a water cooler or ask for the town water to be connected....