Our Aquascape pond is 3 1/2 years old, and now looks as if it needs
cleaning. The pebbles that cover the entire pond and streams are
covered in algae and look unsightly.

We have had two cleaning estimates: One proposed power washing the
rocks; the other said that the algae on the rocks should be left
alone, but the sludge under them needs pumping out, which would
involve hand-moving all the pebbles down to the liner. This second
proposal is very expensive.

The two approaches seem to be contradictory: one says remove the
algae, but leave the bottom sediment; the other says remove the
sediment but leave the algae.

The main concern is the fish. What kind of cleaning is better for
them ? Or can we safely just leave it alone ?