Rehabilitating my pond

seandgh

Hello everyone. I am after some advice about how to best look after the pond in my garden. It’s a natural pond that I am fairly sure needs dredging but not at all sure how to go about it. I get in it a few times a year with waders on and try and reduce the amount of weed etc. Recently that duck weed, Lammas is it?, has been a problem, although in previous years we’ve had loads of some kind of white Lilly that is prolific, and also we have a couple of broad leaved Lilly’s, with beautiful flowers that occasionally show themselves. When I am in the pond it is clear there is a lot of sludge on the bottom. There are over hanging trees that I should probably reduce but that’s quite a job. Another indication of an over abundance of rotting matter on the pond floor is that when I am moving about in the pond when I am in it, there is often a rotten eggs smell. Guess I shouldn’t light a match! The water levels are down now and the far end of the pond is basically sludge to the surface.

I want to do something that is good for the wildlife, yet will also restore the crystal clear water that I remember we had for a several years after moving into the house. I imagine the correct time to do anything is Autumn. We do have lots of newts and toads. There is also a tiny artificial island in the pond and I once remember seeing an eel tumble off it into the water… I kid you not. We’ve also had mallard ducks nesting on the island… 10 or so ducklings this year, although I don’t really know where they went. Last year one was left behind and we had to look after it for a while - lived in our shower for a while - because it was right in lockdown and we couldn’t get any help from wildlife organisations.

Anyway, I attach a few photos and hope to get some useful suggestions.

Sean

Posy

I'm very jealous! I think, as you say, you need to get in there and dig out some of the sludge, but timing is difficult. All the frog and toad tadpoles should be gone by now but newt babies are still very tiny. Some amphibians will return to the pond to over-winter so I would guess late summer or early autumn is best.

When I have a go at my much tinier pond, I scoop up the sludge into wide containers. Anything living can be pulled out and put in a safe place until later, but working on something so much bigger, you may have to accept some losses. Add the sludge to your compost heap.

The plants could be reduced then, too. Monty Don just did a feature on thinning out pond growth on GW, a messy but satisfying job. The duckweed is really hard to get rid of - do ducks eat it? Your ducks will have added waste to the pond, also suggesting a good clean. We had one live with us for a year or so, once, and it just about destroyed the pond and really muddied the water, but it did clear after a while.

Good luck.

seandgh

thanks @Posy, I am itching to get in the water and do some dredging but I think I had better wait until autumn when it will hopefully cause less harm to the ponds inhabitants. I guess it will be a voyage of discovery... how deep to go, what to do with the dredgings. Well I guess I'll cart the muck to the side of the pond and then take it from there down to the compost heap. Its probably super nutritious... which of course is the main problem! Thanks for your response anyway. I am hoping some other forum members will chip in... I need all the advice I can get!

Astraeus

I can't quite make out from the photographs but is the entire surface covered in algae/duckweed or something similar?

Given the smell, I'd say that you do need to clear the sludge (although some is helpful/inevitable). I'd be tempted to clear the lot out to start afresh with the intention to keep on top of it. It sounds like what's in there now is decomposing to cause the stench.

If the surface is covered, plants that will help you maintain water quality simply won't grow. They've been outcompeted by the algae and need a helping hand. Once it's clean, a good mix of plants to take up the nutrients that the algae has thrived off would be worthwhile.

seandgh

@Astraeus it’s not entirely covered by weed but there certainly is a lot of it. The smell is only when I am in the pond and disturb the bottom, there’s no smell otherwise. The border of the pond had Arum Lilly , irises, marsh marigold and various other things. The irises are quite prolific and get more each year. The pond is probably 15 to 20m long and pretty deep in some sections. I’ll try and get some better photos, I agree it’s difficult to get an idea of the situation from the ones I have posted.