Please help me fix it

It’s just heaving with brown mulmy crap!
I have tried to clear it by hand but it’s so fine it just disperses and makes the water murky...
There are loads of newts resident which breed every year so they seem happy enough but I’m worried the mulm is going to cause issues, I keep reading about it reducing oxygen for example.
Plus it just doesn’t look very attractive!
There’s no filter because it’s a wildlife pond.