"M Walczak" wrote in message
hlink.net...
I have tap water and my kh is about 16 in a heavily planted tank 29g with
diy co2, gh 12, ph 7.7, NH3 0, NO2 0. How should I go about lowering it
safely? I may know the answer to my own question but I am not a very
confident aquarist quite yet. But how about doing week water changes? Up
to
what percentage would be safe to do weekly? My tap water has a kh of
about
4. Yes I'm not sure how my KH got so high, my tanks only been set up for
3

Depends on what fish you have in there......as a general rule, little &
often. Of course if you are trying to reduce anything through small water
changes the more water changes you have to do.

In practice you could do a couple at 10% & then a few days later do 20% &
then maybe 30% & then anything upto 50% as many times as you need to (always
a few days apart) - if you work it out the rate of change in the KH is not
linear after the first change.....

ie after the first 10% change you have 90% old water & 10% new water
after the second 10% change you have 81% old water & 19% new water
etc etc....

By the time you have changed half the water when you do a 10% water change
you are only actually changing 5% in effect if that makes sense.

As to why it has climbed so high, you have a source of Calcium carbonate in
the tank - probably a rock. If you have rocks in your tank take them out &
test them with Vinegar - the one that fizzes is the culprit.

I.