Dear Sven,

My pond is overgrown with water plants and slime. I want to give it a good clean, but how do I do this without upsetting my fish and pond life too much?

Thanks for your help,

Simon

Our Gardens Expert replies:

Hi Simon,

Large ponds can be left uncleaned for around 10 years, but smaller ones should be cleaned every four or five years to keep them from filling up with silt and rotting vegetation. It also gives you the chance to check the liner for leaks and divide and split plants.

The best time to do this is the late spring when the plants are happiest being split and replanted. If you have a wildlife pond, I would suggest doing it in the late winter when there is less activity from the wildlife and therefore less disruption. Set a whole day aside so it can be done in one go which will be less stressful for any fish you may have.

The first step is to get some kind of holding tank ready to keep any creatures and plants in whilst you clean the pond. Ideally, this would be a large fish tank, but a paddling pool would do the job. Fill the holding tank with some water ideally from the pond if it's not too filthy.

Now you can start to drain the pond. Hiring a pump to do the job is by far the easiest way and, as the water level falls, scoop out any 'little critters' with a net and put them in the tank. Also remove the plants to the holding tank too.

Now is the filthy bit! Get your wellies on, get into the pool carefully and start scooping out the silt in the bottom onto a tarpaulin on the side and leave it there for a while so if you scooped up any creatures they can get back into the pond or hide until you are done. Then check and clean the liner for tears and if there is a pump, give that a good clean as well.

You are now ready to fill the pond back up. Take a good scoop of the silt and chuck it back in the bottom (it will be full of micro-organisms that will be re-established in the pond). I would also save the water from the holding take and put that back for the same reason.

Refill the pond and re-plant, dividing plants where necessary and re-potting as you go; then replant the marginals. Finally, return the fish and any other wildlife.

Good luck!

Sven