GH vs. KH & pH levels

To: Aquatic-Plants at actwin_com
Subject: GH vs. KH & pH levels
From: George Booth <booth at hpmtlgb1_lvld.hp.com>
Date: Mon, 12 Jun 1995 10:12:33 -0600
In-Reply-To: Your message of "Sun, 11 Jun 1995 15:39:04 EDT." <199506111939.PAA09615 at looney_actwin.com>
> From: AAronson at aol_com
> 
> My tank:
> 37g, 5.5pH, KH 0ppm, GH 107ppm (according to Tetra test kit).
> 
> Water changes are done using distilled water 'fortified' with Aquarium
> Pharmaceuticals "pH Adjuster" and "ElectroRight".  Needless to say, I can't
> seem to raise my pH above 5.5 no matter how much pH Adjuster I add. I imagine
> this has to do with the lack of KH. So, herein lie my questions:
> 
> 1) What is the difference between KH and GH as according to the Tetra kit?

The "KH" test kit measures the total alkalinity, of which "carbonate
hardness" (KH) is a major contributor.  KH is the measure of
bicarbonate (HCO3-) and carbonate (CO3--) ions in the water.

GH is general hardness and is the measure of primarily calcium (Ca++)
and magnesium (Mg++) ions in the water. 

> 2) Which one more closely relates to the 'hardness' spec I read everywhere?

GH

> 3) Instead of using the Aquarium Pharmaceuticals additives, what other
> products (from Kent) would I use? (RO Right for hardness, Freshwater Trace
> Elements for trace elements and ??? for pH)

You might try a mix of distilled and tap water to get some hardness.
I don't know what commercial products offer. 

> 4) What can I do in the mean time to raise my pH and KH?

Try adding some baking soda (sodium bicarbonate).  It will raise your 
KH and pH. 

One teaspoon (about 6 grams) of sodium bicarbonate (NaHCO3) per 50
liters of water will increase KH by 4 degrees and will not increase
general hardness.  Also, two teaspoons (about 4 grams) of calcium
carbonate (CaCO3) per 50 liters of water will increase both KH and GH
by 4 degrees.  Different proportions of each can be used to get the
correct KH/GH balance dictated by the fish and plants in the tank.
Since it is difficult to accurately measure small quantities of dry
chemicals at home, a test kit should be used to verify the actual KH
and GH that is achieved.

> From: gomberg at wcf_com (Dave Gomberg)
> 
> If you just add distilled water to your tank, the pH would normally
> drift closer to neutral (if you were making up for water changes or
> splashing) or stay the same (if you were making up for evap).  

NO NO NO NO NO! (Sorry about that fit of vehemence)

Pure water may have pH of 7.0, but it has no buffering capacity and
will be easily pushed to high or low pH values by the smallest amount
of acid or base in the water.  In an aquarium, the biological
filtration cycle is essentially adding nitric acid to the water, which
dissociates into NO3- (nitrate) and H+ (causing the pH to drop).  If 
there is no buffering from carbonate hardness or "evil" phosphate
buffers like pH-UP or -DOWN, the natural tendency of an aquarium with
extremely soft water is to have a dangerously low pH. 

> As it is you are adding chemicals, something I would NOT recommend
> until you understand what is going on.

Umm, water is a chemical.  Everything is chemicals.  :-)

George