Hal,

It sounds like your filter is working very well, and it does keep the large
debris out of the system. If you have enough limestone, as the pH starts to
drop, it will start to dissolve and buffer the pH. It is solid KH, and is
hard to measure with a test kit, since it is not in solution. If your pH is
relatively stable and you haven't crashed, you may have plenty of the
limestone. My importer uses oyster shell for the same purpose, and nearly
half of his filter chamber is filled with oyster shells. BTW his filters
are nearly as large as his tanks.
--
RichToyBox
http://www.geocities.com/richtoybox/index.html

"Hal" wrote in message
...
On Tue, 24 Aug 2004 01:18:36 GMT, "Richard E. Steele"
wrote:

I wish that I could have the submerged plants to provide some of my
buffering, but the fish would eat it all. Right now, I am using an
upflow
filter of crushed oyster shell and baking soda.

I'm crushed! I thought I was on the brink of discovering something
new and workable. I've been using garden lime for several years now
and a couple years ago I added lots of baking soda and gypsum to raise
the KH, but I created a great environment for string algae so I
stopped the baking soda and gypsum. The limestone stops dissolving
when the pH gets to 7.8 and my KH hardly gets up to 3 degrees. The
rainfall has become so acid, every time it rains I wonder if this
will be the incident that causes a pH crash. So far the limestone
seems to be preventing a crash, but my KH readings are way below 100
ppm. I could use some submerged plants.

The wood box that I built for a plant pond is beginning to rot and sag
so now I'm thinking about rebuilding it into two plant ponds, one for
floaters and one for submerged plants, but that still leaves the
problem of keeping the submerged plants from floating out and keeping
the bottom clean. When I took out the gravel out of the plant pond I
made a sweeper from a pipe I ran along one side of the bottom and it
seems to keep the bottom pretty clean. The only thing there after
several months is some empty black Japanese snail shells and the
clinging algae.

My filter isn't anything to brag about. It is, gravity flow, three
barrels the first made to circle the water and settle the heavy stuff,
the second has a few squares of 3/4 and 1/2 fence mesh backed by a
window screen which needs cleaning every week and the third contains
the pump, but my weekly readings are 0 ammonia, nitrites and nitrates.

Regards,

Hal