clearing sludge at the bottom of the pond

[whathaveiforgottentoday]

Hi, I
moved to a house with a reasonably sized wildlife garden last year. Managed to get the pond sort of under control (full of oxygenating plants, lots of wildlife although i think the heron ate most of the frog spawn) but .... if I poke around in the middle of the pond it still has a considerable amount of sludge which is anaerobic (bubbles of nice so nice smelling gas comes up if i poke it around. Rest of the pond seems quite healthy now.
What is the best way to get rid of the last of the sludge?

We waited till winter and used a bucket to scoop it out. We left on the bank so that any wildlife could slither back into the pond.

If it's a wildlife pond you'll probably bet to leave it until at least late autumn or early winter.

Tbh I'd just leave it as it is.