The filter bacteria consume KH, and if the KH drops to around 40 pH crashes
are imminent. For the bead filters, they really need KH values over 120 and
values to 300 are not detrimental. If the KH is constant, above 100, the pH
is pretty stable. As for the use of the sea shells, they are calcium
carbonate, and will only dissolve when the pH is pretty low. They do an
excellent job of preventing pH crashes, if there is sufficient quantity
available, but they also release calcium which makes the water harder.
Baking soda will raise the KH without raising the GH hardness. If you are
getting the high GH values due to the dissolution of sea shells, then more
frequent water changes would be in order.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"billfish" wrote in message
...

RichToyBox Wrote:
Hard water is really not a problem.

Sorry. When I typed in my post I didn't realise this forum doesn't
support "more than" arrows. It should have read that the GH is more
than 16, i.e. off the scale on the test strip and classed as very hard
water. I was a bit concerned because, from what I've read, for most
fish, including GF and Koi, moderate to fairly hard water is
preferable. When you say the KH is at the low end, what should it
ideally be? I live on an island, so seashells to put in the filter are
not a problem for me if you think it is required to raise the KH.

Bill.


--
billfish