Silted up pond

I have a two-level triangular pond (approx 20' each side overall) which has
become very silted up with dust and muck blown in through the winter.

I have been quite diligent in removing leaves: it's the fine particle stuff
that is my problem.

The water is clear (I have a sturdy pump/filter which runs 8 hours a day)
but a lot of the muck that is building up on the bottom is not within the
pump's collection range.

Currently, as well as a good stocking of plants, I have frogs, tadpoles and
at least two species of newt co-existing quite happily with visiting
dragonflies etc etc.

All very "in balance" but the muck level is rising and I do need to get
quite a bit of it out with minimal impact on my wildlife.

Can you recommend a suction device with an effective front-end filter that
would shlurp up the muck but leave the tadpoles and other wildlife
unaffected?
--
Brian
"Fight like the Devil, die like a gentleman."