Lee,

I like to keep mine higher than 100 also. I try to maintain a minimum of 10
degrees, about 170, but I start to worry when a pond has less than 100. 300
or 400 won't hurt a thing.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Lee Brouillet" wrote in message
...
Further to that, the reason a large plant mass will reduce KH is because
photosynthesis reverses at night: the plants produce CO2 instead of O2.
CO2
is acid, thereby reducing KH (and the reason why your pH is always lower
in
the early AM than it is towards sunset).

I'm not trying to disagree with RTB about the level at which to keep your
KH, but if mine - for my area - was only 100, I'd be susceptible to a
crash.
Rain here in Central FL can be quite acid: on Monday, I received 2 1/4
inches in 20 minutes, and it dropped my KH by 3 points (~ 60 ppm). I would
have been in deep kimchee if I didn't keep my KH higher. Besides,
bead-type
filters *require* KH higher than 200 to work properly and feed the
bacteria.

Lee

"GD" wrote in message
news
"RichToyBox" wrote:

GH is a measure of the calcium and magnesium in the water. A high
number
is
good for bringing out the black in koi, but is said to cause shimmies
(unwanted black marks) in the red.

KH is a measure of the carbonates and bicarbonates in the water. These
are
used by the bacteria that digest the ammonia and nitrites, and as such
it
will go down. When the KH gets low, the pH will crash. You can get
high
GH
and reasonable KH with limestone, or oyster shells, but these are slow
dissolving. You can increase the GH with plaster of paris. To get a
good
KH and get it quickly, use baking soda. If you have a high (over 100
ppm)
KH your pH will be solid and their is no reason to run it, except for
information.

Note: some submersed plants (frequently referred to as oxygenators in
this group) will use carbonates and bicarbonates as a carbon source
for photosynthesis. A large biomass of plants can reduce KH in short
order, as can algal blooms. If you keep submersed plants and fish
together, follow RichToyBox's recommendation that you monitor KH;
drastic changes in pH between afternoon and morning may indicate
reduced buffering capacity of your pond's water, something that may be
remedied by amendment with calcium carbonate, sodium bicarbonate, etc.