Dave Millman wrote in message ...

You did not specify how long it was between water changes. KH is consumed
by normal biological processes in a planted tank. KH drops by 0.2 to 0.25
per week in my tank. This explains your KH drop. Baking soda raises KH and
nothing else, and is the simplest way to raise KH.

Ah! That's very helpful to know; thank you! Averaging 1.5 weeks
between water changes, but I'm not extremely predictable.

A rise in GH is probably caused by something dissolving in your water.
Leading candidates are rocks or some component of your gravel. If KH
falls, pH falls with it. This causes the water to be more acidic, and
could cause more rock material to dissolve.

Hmm... okay. I use Seachem Fluorite exclusively for the gravel,
which I understand to be pretty much totally chemically inert.
(PARTICULATE-ly inert would be another story...

1. Get on a regular water change schedule. 20% weekly is good, or biweekly
at a minimum. Use a water conditioner (Prime or Amquel).

Are there issues with too much Amquel? Why would I want to treat RO
water with Amquel? I do use the designated proper amount whenever I
add tap water in since we have chloramines here.

2. If you want to continue using RO water, supplement it with Kent RO
Right and baking soda to restore GH and KH. Other products work too, but
RO Right is much cheaper in the long run.

If I understand correctly, reduction of salts dissolved in the water
notwithstanding, RO Right is a replacement-water deal. Is it also the
case that I can gently approach my desired GH with small doses of RO
Right every day?

Thanks for your time,

Ben