Okay, found an interesting thread on the koi vet board
http://www.koivetforums.com/forums/s...3&page=2&pp=15

and

Koi Clay is a naturally occurring calcium bentonite clay, which is available
from only a few of the bentonite mines in the world. It dissolves well and is
ideally suited for recirculating koi and garden ponds. 100% all natural. It
contains a balance of minerals in their natural colloidal form, making them
easily assimilated. They enhance the production of enzymes in all living
organisms, improve water quality and removes toxins from pond water. They
benefit both plants and fish as well as the "good" bacteria living in your
filters.
(from this commercial site
http://www.pondbiz.com/home/pb1/page_696/koi_clay.html

and

BENTONITE*
Definition :
Bentonite is a special type of clay that pocesses some properties which make it
of economic importance specially in drilling operations for oil or underground
water . it absorbs great amounts of water and increases enormously in volume ,
acquiring the colloidal property needed for the drilling mud .

BENTONITE
Hydrated Bentonite is a natural clay, which comes from volcanic ash.*


13. Add bentonite clay to large or koi ponds.* The clay acts as a coagulant
and settles out algae.* It will cloud the water in the short term but will
shortly thereafter clear up.* It also benefits the koi by providing minerals.

and

Unhappy with the inconvenience of traditional litters, biochemist and cat
lover Thomas Nelson began investigating alternative clay formulations in the
early 1980s. He observed that a certain type of clay called bentonite clumped
up in the presence of moisture, allowing waste to be isolated and scooped out,
leaving behind clean litter. Today, roughly 60% of the cat litter sold in the
U.S. is of the clumping variety, and most of it is made from bentonite clay.
Bentonite is largely composed of montmorillonite, a clay mineral made up of
stacks of SiO4 sandwiched between two sheets of octahedrally coordinated
aluminum, magnesium, or iron. Substitution of lower valence ions for some of
the higher valence ones in the octahedral sheets creates a negative charge
imbalance that traps cations, most often sodium or calcium, between the stacked
sandwiches.

Also found that some folks ingest this stuff to clean toxins from their
systems! eekk! ;-)

Now I've *got* to pack to drive to Seattle, this is a quick trip but I'm going
to try and visit one nursery while I'm over there and look for pond stuff!


kathy :-)
A HREF="http://www.onceuponapond.com/"Once upon a pond/A