Why are my pond plants and animals dying?

[croomes]

We finished digging our wildlife pond last May and filled it with native pond plants (water forget-me-not, water violet, flag iris, spiked water milfoil and hornwort). We got the usual invertebrates and other pond creatures in really quickly and have had healthy populations of water snails, water beetles, worms of some description, caddis fly larvae, mayfly larvae, pond skaters, etc.

By the end of last year however, the hornwort had all died. This spring the water violet has disintegrated and the water forget-me-not has become very leggy and is only just holding on. The flag iris grows to about 6-8 inches high and the leaves go brown and they die off. The only plant that seems to be doing really well is the spiked water milfoil, which leave it as the only oxygenator in the pond.

Up to about a week ago the water had been quite murky after the winter and all the recent rain. We then got some strange green globules on the surface of the water, which looked like green oil paint. The next day however these globules had gone and the water is now the clearest we’ve ever seen it; in fact we can see the bottom of the pond for the first time since we filed it with water!

We’ve never suffered from blanket weed or duckweed. We had a healthy and successful breeding by the pond skaters this year but we seem to have a myriad of water boatman that have successfully hatched. All our water beetles have gone or died, except for one very large one. All the wormy things, the various fly larvae and the water snails have all gone as well.

We haven’t added any tap water and only top up with rain water from our water butt. We’ve not added any fertiliser or any other type of additives to the pond.

Can anyone explain what might be going on or why the plants have died and the invertebrates have disappeared as we’re getting a bit worried?

Many thanks in advance.

[Kayleigh]

It sounds like the water is polluted. The water may not be discoloured or smelly the key feature is that it is harmful to plants and fish/insects. There are several forms of pollution.
An oily film may develop due to decomposition of water lily and deep aquatic foliage.
Black water indicates fallen leaves or dead fish.
Or there maybe other things like weed killers or other harmful chemicals that have got into the water.

[djackso]

I agree with Kayleigh, also I did once read water from the water but can be stagnant and contain poisonous algae and such.

[BREnvSciGang]

I suppose that if it was left in the water butt for a while it may get stagnant...?

Such information would be very useful for us as we are designing a pond for our conservation area and we are trying to think of where we can get the water from. In another post someoen said that they started their pond with water from another pond. Is this a good idea?

[djackso]

I've now made several ponds - some more successful than others.
But I only know what works for my ponds and my garden.

(And I've had plenty of ecological disasters of my own, but that's another story. BTW a product called something like "Sludge buster" has helped in the past.)

I would recommend a "starter culture" from a healthy pond - yes definitely.

I check the health of my pond by looking at the daphnia etc - I think the more the merrier. If your other pond has plenty - I think I'd trust that water.

Avoid fish - I would never add even stickleback back to my main pond now - even though they are supposed to be ok.

I recently relined my main pond, I reserved all the water that I took out (luckily I DID have a container big enough - but the pond is fairly small - 2 m across). I let that settle. When I filled the new pond (during very rainy weather) I used a mixture of FRESH rain water straight from the butt and the water from the old pond - now without most of the sediment.

I cannot believe how quickly everything has established - there is no green water, no blanket weed ( the scourge of previous attempts), and loads of life - infact too much - so I introduced some predators to keep everything on its toes.

Hope this helps.

[croomes]

Thanks for all the replies so far. I'd like to clarify a few things though so we can try to narrow the problem down a bit.

An oily film may develop due to decomposition of water lily and deep aquatic foliage - there is no oily film, nor have we have one, except for those strange green oily gloubules which came from nowehere and have vanished as quick as they appeared.

Black water indicates fallen leaves or dead fish - the water isn't black, nor has it ever been.

Or there maybe other things like weed killers or other harmful chemicals that have got into the water - we don't use any chemicals or weed killers as we garden specifically for wildlife.

I'm intrigued about the water butt issue though, as most of the pond books I've read, as well as forums on the internet, suggest that if you do top up during the summer, to use rainwater from your water butt. We did swill our butt out with clean water before last winter to make sure it didn't contain anything nasty, so unless something has fallen in the rain I can't see what it might be.

Could a bird have picked up something nasty from another pond and transferred it to ours? We do get the blackbirds and wood pigeons bathing in the pond - after all that's what it's there for!

I've also read that it can take a good one-three years for a new pond to really settle down and for everything to be OK. Could that be what's happening and we're having a little blip?

Cheers for now.

[Kayleigh]

I still thing something nasty has got into it, to kill off the plants like this.

Maybe something from a neighbours garden.
Like slug pellets, rat poison ect. Then a frog or other form of wildlife could have brought it to your pond.
I have made all the suggestions I can.

[djackso]

What sort of roof do you collect your rainwater from?

We collect from a plastic roof with a small amount of metal flashing (not sure of the composition - but it's turned out ok).

I would be worried about collecting from newly laid "felt"/bitumen or anything with new cement - which is very toxic.

Do you get plenty of sunlight at the pond?

Having some microscopic plants/algae is very important - they are the all important first link in the food chain that feeds life to the pond - it's absence is very worrying.

Remove as much dead material from the bottom as you can. You could ask an expert at a water garden centre if there are any products to help. There are kits to test the water.

My personal opinion is that you should remove the water/sediment and start again - tap water can be a big problem in that you get too much algae - this is the problem that happens in the first few years, as far as I know. But this problem sounds better than the one you have. Don't stock the pond with plants for several days until the "chlorine" has gone, then have a mix of oxygenators (lots) and aim for 1/3 coverage floating leaves, as well as marginals, then introduce animals slowly after that. Watch them as you add them - they should appear healthy in the new water.

Good luck.

[djackso]

PS Animals do transmit diseases, which may affect one or even several other species - but you've got widespread problems affecting a range of organisms from plants to animals - biological agents are unlikely to be your (only) problem.

[paddy]

I think i'd be tempted to buy a water testing kit (usually for fish tanks). I used water from a butt to do a partial water change in a fish tank last year, and killed several fish and plants. When i tested the water, it turned out to be highly acidic.
A solution to the current problem might be to carry out a similar action to fish keepers - a partial water change, after having tested (for pH, nitrites and nitrates) the source water...