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Re: Lowering pH when adding hard water nutrients to soft water

In a message dated 9/1/00 2:33:30 PM Mountain Daylight Time, 
booth at lvld_agilent.com writes:

<< > To keep it as simple as possible, I recommend you reduce the sodium 
> bicarbonate to give you a KH of 3.  The more you have, the harder it is to 
> move pH down.  Then use simple hydrochloric acid to bring the pH down.  This
> way the only negative ion you are adding is Cl -, which is not a problem at 
> the levels you will end up with.  

I'm puzzled, confused, ignorant or perhaps all three to various degrees. 

KH adds bicarbonates to the water as well as sodium ions. Bicarbonates are a 
buffer. When you add acid to water with bicarbonates, the H+ ions generated 
the acid dissociates combine with the bicarbonates to form, um, water, CO2, 
But the end result is that bicarbonate is "destroyed" by the act of 

So you add "too much" sodium bicarb and the pH goes above where you want it. 
Then you "neutralize" the excess by adding hydrochloric acid to get the pH 
down to where you actually want it (by reducing KH!). 

So, the end result is you now have extra sodium and chlorides. Is this the 
Jeez, why not just add salt - it cheaper and safer. 


I agree.  It is hard for newbies to get the balance and learn when enough is 
enough.  Susi has a significantly unique situation where there is no 
measureable calcium, magnesium or carbonate in her water.  Personally, I 
would die for that but she doesn't like it for reasons she stated and 
justified well.  So she wants to add some stuff.  If she limits the amount of 
NaHCO3 then she won't need so much HCl.  Personally, I would stick with the 
dolomite, which gives a good balance between Ca and Mg, and also adds 
buffering.  Another good option would be an electrolyte mix like RO-Right 
designed for use with RO or DI water.

At any rate, any addition of carbonate will swing the pH upward.  If she 
wants to get it back down, she needs to find a good pH rducing agent.  Muriati
c is the cheapest and the simplest agent I have found to date.  

Bob Dixon
Cichlid Trader List Administrator        o
http://cichlidtrader.listbot.com               0