"LeighMo" wrote in message
...

Can you ask them? Or search online. Many localities have their water
reports
on the net. Search on the name of your locality and "water report"

I do have the water report. I'll have to see what they add to make the pH
higher..

And are you sure your KH test kit is working? Does adding baking soda
increase
your KH?

I'll have to add baking soda and see what it does (have done it on pH
indicator, but not on KH). the test kit is new, so..

Tank is can be regarded "moderately low light". I have ~5400K 55W CF
(37G)
with the metallic reflector, sitting on top of a glass hood (Versatop).

So it's 55 over a 37 gallon tank, plus natural light?

yes

That isn't a lot of light, but some people have had pH problems even with
moderate light. (Probably it depends on how many plants you have. Plus,
the
first couple of weeks, PCF bulbs are extremely bright. They dim down a
lot
after that.)

the bulb is 3 months old.. so I think (if I read all the FAQs correctly) I
have about another 8-9 months before I have to replace it...

Try measuring the pH in the morning, just before the lights go on, in the
middle of the photoperiod, then in the evening, when the lights go off.
If the
pH is lowest in the morning, then rises all day to reach a peak at the end
of
the "day," then the plants are the cause of your pH changes.

ok

If the pH gradually rises over several days while the KH drops, again,
it's
probably the plants.

KH is pretty similar to the tap.. so it seems like KH is stable..

the gravel I use is supposed to be inert
(50% epoxy coated, the other 50% is natural)

The epoxy coated should be fine, but what's the natural gravel?

it looks like smooth rounded quartz-based stuff with other stuff in it (no
fizzing when I put it into vinegar, etc). natural rock color that they sell
at LFS (white quartz, rose quarts, brown, reddish brown...) sort of a
natural light-colored rounded pebbles. just not coated (the epoxy coated
one is more darker reddish browns).

linda