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Re: pH, KH

> From: damon at babylon_icd.teradyne.com (Damon Fisher )
> Subject: pH and KH levels
> Hello-
> Is there anybody who can give me some advice on maintaining proper pH and KH
> levels? 

	In short:

	Check that the pH, KH and CO2 concentration you want are mutually
compatible and acceptable for the fish.  Use the usual tables for that.

	Use bicarbonate (either as baking soda or as calcium carbonate,
which will take a while to dissolve and become bicarbonate) to set the

	Use a CO2 system to get the pH you want.

> I've read about the dangers of having a low KH (lower than 2 causing pH instability). So, I added a carbonate hardener (contained carbonic acid in powdered form). 

	That probably means it was sodium bicarbonate (baking soda) at a 
price about 100 times higher than usual.

> I think the name brand was called BufferUp. My pH started
> rising. 

	As it should if the KH is increased.

> I started out with KH=1, pH=7.2, GH=7, CO2~25ppm.

	Check the tables in the Krib.  KH 1 and pH 7.2 indicates CO2
of less than 2 ppm.  Something is wrong with your measurement of something.

> I reached a KH of 4 but the pH went up to 7.5 

	A factor of four increase in KH should increase the pH by 0.6 (log(4)).

> (the product claimed pH would not 
> be affected).

	Demonstrating that the manufacturer had no understanding of this.

> I started to add a nonphosphate pH reducer. When I got the 
> pH down to 7.2, the KH started to reduce to 2.

	The nonphosphate pH reducer was probably sulphuric acid, which
would destroy KH (bicarbonate).  You reduced the KH by a factor of 2,
and the pH fell by log(2), which is 0.3.

> My target is: KH=4, pH=7.0, GH=7.
> How can I get a pH of 7.0 and a sufficient KH of say 4 (for pH stability)?

	You need a CO2 concentration of 12 ppm to do that.

> I left my tank alone with the following current conditions (the fish can't take the ups and downs of the pH/KH):   KH=2, pH=7.2, GH=7, CO2~50ppm

	If the pH and KH numbers are right, the CO2 concentration is
actually about 4 ppm.

> I have a planted 45 gallon community tank. Some plants/fish prefer slightly
> above 7pH while the others prefer 7.0 or slightly below. I'm thinking of adding
> a DIY CO2 system. Does the KH have a direct relationship to pH?

	Of course.  Double the KH, increase the pH by 0.3.

	If you don't have a CO2 system now, the CO2 concentration is much
more likely to be 4 ppm than 50 ppm.  Add baking soda to increase the KH
to 4 and add a CO2 system.  Stop throwing in unknown chemicals.

	As a probably perfectly acceptable alternative, do nothing except
reasonably frequent water changes.  KH 1, pH 7.2 will probably suit the 
inhabitants just fine.  The water changes will ensure that the KH
doesn't fall to near zero, provided that the water introduced has KH 1.

	Once again, do not throw in unknown chemicals.

Paul Sears        Ottawa, Canada