Help me reconstitute r/o water...Please!

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undbulsu

Aquarium Advice Apprentice
Joined
Jan 25, 2005
Messages
36
Location
Lexington, KY
As I have a ready supply of r/o water I want to use it in my planted tank. It is heavily planted, with @ 3.5 wpg and Co2 injection. I try to maintain a pH of 6.6 and a kh of 3, giving a Co2 level of @ 22. I use Kent's r/o right to adjust the gh and that is working fine.The problem arises when I try to add something to raise the kh level in the r/o water. Obviously adding an alkaline buffer will raise the kh and ph. (I use Seachem alkaline buffer). If I then add Seachem's acid buffer to set the desired ph, the kh levels are too low. I understand the relationship between kh/ph and co2, but what should I try to match to my desired levels?
A. The kh and then let the co2 in the tank drive down the ph?
B. Add both alkaline and acid buffer to obtain the desired ph, and don't worry about the kh?
or
C. Use something else to reconstitute my R/O water?
 
Ok, you can't raise Kh without affecting pH...they are inter-related.

Why would you raise the Kh then lower the pH with an acid buffer? That makes no sense. CO2 lowers your pH. If you use an acid buffer to achieve a lower pH, then you've skewed your Kh/pH relationship, and have a lot less CO2 than you think.
 
Thank you malkore, that's what I thought.

I was just wary about putting water with a significant ph difference into the aquarium. I understand the kh/ph/ co2 relationship, and I guess I should have been clearer in my question. In any case thank you.
 
I'm in a similar but somewhat opposite situation. I keep African cichlids in my planted tank (or is it plants in my African cichlid tank?) and I need to maintain a fairly hard (KH ~14) water condition. I first use sodium bicarbonate to adjust the water to 14 dKH and then inject CO2 until I reach 7.2, which is about 30 ppm. You can pick your KH or you can pick your pH, but you can't pick both if you want to maintain proper CO2 levels.
 
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