Pond gone stagnant

[kath99]

My 3 year old pond has gone stagnant. Usually the water is clear and smells earthy. Now it smells rotten and there are mosquito larvae in it.
I'm not certain, but here are a number of factors that might be relevant:
1. The plants surrounding the pond now cast a lot of shade.
2. I cleared out a lot of oxygenating plants a few weeks ago.
3. The is a lot of duckweed.
4. This year black willow aphids have dropped a lot of dew on the pond surface
As the pond - which has no fish in it - is 3 years old now we were going to give it a good clear out and restock the plants this autumn. But it is sad to see it in such a poor state right now. I don't know much about keeping ponds. I like wildlife and (probably) won't be putting a pump in.
I would like some advice please.

[MustafaTickl]

Somethings lurking on the bottom?

[Kleiber]

Did it start to go stagnant after you removed the oxygenating plants? If so, then that's it. Mine went really cloudy & murky for a few months during the spring/summer, although there was frogspawn there. I just left it & let nature take its course and after all the recent rain, it's now lovely & clear again! I haven't had mossie larvae though - I've a lot of pond skaters, water boatmen & snails in mine, also dragon fly larvae & water beetles. Try putting a small bale of straw in - that helps it clear. And scoop out the duckweed - horrid stuff - keeps the light from the water & that's what makes it go murky.
Do you have overhanging trees?

[RATTER15]

Put in a pump and filter, it will improve water clarity and encourage plant and wildlife, it doesnt have to be a fountain just something to cause a little movement in the pond!!

[someguy0000]

ive got a medium sized pond and duck weed is a pain.......... i do have lillys in there though and a pump i think for any pond is a must ,although ive been told is not completely necessary.fish will eat the larvae as well ....lots of plants again and see what happens.......all the best :)

[elliottpowow]

To amplify what others have said - I do recommend barley straw - now quite widely available - it really helps. Don' t pay too much for it at a posh aquairium store, look for it in cheapo general stores.
Latest advice I've received is that water snails don't have any beneficial effect in ponds, they just look nice, If you think so!