Hi

I have had a small pre-formed pond for several years and have cleaned
and repotted the plants and lilies from time to time with no problems.

After repotting the plants last year in some particularly dark '
aquatic soil ' the pond has gradually accumulated more and more dark
sediment that regularly clags up the pump and filter. I was hoping it
would disperse but in fact it has got worse over time and although it
doesn't appear to harm the fish, I'm sure it inhibits lily growth.

I have now decided to try and get rid of all this black muck, cleaning
the pond, baskets, pump and filter box as best I can.

Bearing in mind this appears to be some kind of organic material that
grows, is there anything I can do to ensure I get rid of it completely
before refilling the pond and returning the fish. I would hate to be
back in the same position, within a few months.

Andy