For a concreted bottom with rock imbedded, the use of a power washer of some
type to clean the rocks would not be a problem. It would remove any algae
that grows on the rocks, which is good for filtration, but if some were
allowed to build on the sides, then it should be ok.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"David" wrote in message
...
Good point Rich.

I should have said that my design will be concrete, with the rocks
mortared down in -- therefore no voids underneath. IMHO, that should
relieve much of the problem because the bottom drains would still be
pretty effective. (Of course not as effective as with no rocks at
all, but still reasonably effective.) AquaScape doesn't even use
bottom drains at all do they?

Given the above perspective, don't you think that the water blaster
wand could work if it was done judiciously? By that I mean, don't
ever let the buildup get out of hand, and even then only do a fraction
of the pond at any one time. (?)

I respect your point of view -- I know that you have been at this a
lot longer than I have!

On Wed, 3 Aug 2005 11:52:36 -0400, "RichToyBox"
wrote:

Unless you remove the fish first, I believe that this would be a very bad
idea. The hydrogen sulfide that is produced in the anaerobic conditions
is
very toxic. Blasting it loose would free the hydrogen sulfide and kill
all
the fish. The main group of installers of gravel bottom ponds have a
requirement that the pond be drained, power washed and restarted each year
to work properly. No rocks makes it easy to keep the mulm from building
up
thick enough to cause the anaerobic breakdown, and it therefore safer for
the fish.