" George" wrote in message
news:RxSHe.214366$_o.1195@attbi_s71...

"JGW" wrote in message
...
We're getting ready to build our new pond. The contractor wants to
line the walls and bottom with rocks, which he says will serve as a
great huge biofilter. I have read that it's impossible to keep the
pond clean with rocks on the bottom, and that they can trap hydrogen
sulfide gas.

What are your thoughts?

Thanks.

Joan
___________________


Some use rocks, some don't. Whether it traps hydrogen sulfide depends on
the nature of the material used. Obviously, if you create a thick silty,
clayey bottom, there is a definite possibility that H2S build up will
occur. If, however, you have good water flow, use large pebbles or rock
in a thin layer (I use 1/2"-3/4" natural-color rounded quartz/chert
pebbles in a thin layer more for appearance than anything else - also the
fish like to root around in the rock), have good filtration, and good
biologic growth, and regularly maintain your pond, you should have no
problems. I think the rock gives it a more natural look. On another
note, if your pond is prone to heavy sludge build up, cleaning can be
tedious, and usually involves scooping up the rock and rinsing it, then
cleaning the bottom. Frequent use of aquazyme or similar products can
significantly reduce sludge build up (the source of sulfide-reducing
bacteria).

That should have read "anerobic, hydrogen sulfide-producing bacteria".