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Re:High KH lowers pH?
- To: Aquatic-Plants at actwin_com
- Subject: Re:High KH lowers pH?
- From: Paul Krombholz <krombhol at teclink_net>
- Date: Mon, 4 Aug 2003 23:22:00 -0500
- In-reply-to: <200308040911.h749B3JY005405@otter.actwin.com>
- References: <200308040911.h749B3JY005405@otter.actwin.com>
* From: "Hopkins, Samuel" <Samuel_Hopkins at marconi.com>
Someone on another one of my groups posted that if you add
enough baking soda to water to raise the KH into the 100's the PH
will stabilize either up or down at 8.4.
If you are talking about German degrees of hardness (dh), that much
baking soda sounds absolutely lethal!
So for instance if you started with a PH of 9.5
and added enough baking soda to get your KH into the 100's your PH would
drop to 8.4.
if you have any pH of 8 or greater, the way to get it down is to add
CO2. Adding sodium bicarbonate adds the bicarbonate ion, which can
lower the pH, but if your plants are utilizing the bicarbonate ion as
a source of CO2, they leave behind hydroxide. You will wind up with
sodium hydroxide. With certain aquatic plants and sunlight, you can
get the pH up to eleven!. You would wind up with a tank based on
water conditions of the Dead Sea. I think there are a few kinds of
algae that can live there and a species of fly whose larva eats the
algae. However, brine shrimp can't live there, and there are
definitely no fish!
Anyone know if this is correct? I haven't gotten the chance to
Unless you have critters in your tank that really enjoy highly
alkaline conditions, don't think of testing it. How are you getting
water that tests higher than 8.4? Is that the pH of your tap water?
I can't see any real reason to ever add baking soda. If you have
very soft, acidic water, you could add some baking soda to increase
the capacity of the water to hold CO2, but I think it is better to
add lime or ground limestone. This way you add calcium and magnesium
bicarbonate, and you are adding two essential macronutrients rather
than sodium, which plants don't need. Also, when plants are
utilizing the bicarbonate ion from a solution of calcium bicarbonate,
you get calcium carbonate, which precipitates out. when plants
utilize the bicarbonate ion from sodium bicarbonate, you get sodium
hydroxide, a strong base, which stays in solution. So, the pH goes
up a lot more when plants are utilizing bicarbonate from sodium
Paul Krombholz in steamy central Mississippi