How thick do you estimate this sediment layer to be? How is this pond constructed? Earthen-bottom? Liner? Concrete?
A good solids-handling pump will remove all but the larger pieces of debris, which will require manual removal. This waste can be spread out evenly in a garden of landscaped area on your property (excellent fertilizer).
You should be able to secure an adequate pump through a rental company. I assume that those exist in the UK.
Thanks so much for your reply. The ponds ground as i figured out so far is very even with an deeper point. I think its plaster or something. Its definitely man made, on the outskirt there is foil visible and then the pebbles. The mud is full with plant stuff and otherwise thick and very dark black, its like earth.
Yes a pump makes sense, that would be the easiest way. I will find out if i can rent such thing...
Thanks so much for your advice
PS. I DID NOT THINK THAT I WOULD EVER BECOME AN EXPERT OF A NATURE POND...ok, life go on...