I'm on a quest now to better understand water chemistry in freshwater aquariums. Eventually, this will lead to CO2 dosing and heavy planting. However, I'm getting hung up right now on pH and KH.
My goal is to permanently neutralize the water but maintain a high KH -- preferably between 8-12. If I can't maintain a high KH but can still neutralize the water and stay near a 4 KH, I'll be content.
My RO water has a pH value of about 7.6 and a KH of around 4 (~75 ppm). I would like to lower the pH to 7.0 without destroying the KH in the process. My fish (Silver Dollars, Clown Loaches, Kribensis, Tetras) are acclimated to the water, but if I can lower it to their supposed "preferred" ph level, I wish to do so.
NOTE: I understand fluctuating pH levels can be lethal and that a stable pH is more important than a "preferred" pH. Right now, I need some knowledge; I'll apply wisdom later.
Dosing CO2 is probably the most direct method of decreasing pH without affecting KH, but that's a temporary solution lasting only for as long as the CO2 keeps pumping.
So, I think I need some sort of dissolved additive.
Carbonates can raise KH without also raising pH. I have potassium carbonate (potash).
However, adding a carbonate to a solution where acids are present forms a bicarbonate and increases pH.
This is where I keep getting stuck, because I only know of one additive which reduces pH -- acids. But, that acid is reacting with the potash to raise the pH.
I've used vinegar, citric acid and pH down. I've tried making the water slightly basic (7.1), neutral (7.0) and even corrosive before adding potash. But every time I add potash to increase the KH, the pH jumps up right along with it.
I've also tried adding the potash first, but [for obvious reasons], I have to use more acid and eventually find myself back at 7.0 with almost zero KH.
What am I missing here? I'm ignorant of something vital.
BTW, all these tests have been outside the aquarium in test tubes, bottles and beakers. I won't be applying anything to the tank until I have a firm understanding of these concepts and plausible repercussions.
My goal is to permanently neutralize the water but maintain a high KH -- preferably between 8-12. If I can't maintain a high KH but can still neutralize the water and stay near a 4 KH, I'll be content.
My RO water has a pH value of about 7.6 and a KH of around 4 (~75 ppm). I would like to lower the pH to 7.0 without destroying the KH in the process. My fish (Silver Dollars, Clown Loaches, Kribensis, Tetras) are acclimated to the water, but if I can lower it to their supposed "preferred" ph level, I wish to do so.
NOTE: I understand fluctuating pH levels can be lethal and that a stable pH is more important than a "preferred" pH. Right now, I need some knowledge; I'll apply wisdom later.
Dosing CO2 is probably the most direct method of decreasing pH without affecting KH, but that's a temporary solution lasting only for as long as the CO2 keeps pumping.
So, I think I need some sort of dissolved additive.
Carbonates can raise KH without also raising pH. I have potassium carbonate (potash).
However, adding a carbonate to a solution where acids are present forms a bicarbonate and increases pH.
This is where I keep getting stuck, because I only know of one additive which reduces pH -- acids. But, that acid is reacting with the potash to raise the pH.
I've used vinegar, citric acid and pH down. I've tried making the water slightly basic (7.1), neutral (7.0) and even corrosive before adding potash. But every time I add potash to increase the KH, the pH jumps up right along with it.
I've also tried adding the potash first, but [for obvious reasons], I have to use more acid and eventually find myself back at 7.0 with almost zero KH.
What am I missing here? I'm ignorant of something vital.
BTW, all these tests have been outside the aquarium in test tubes, bottles and beakers. I won't be applying anything to the tank until I have a firm understanding of these concepts and plausible repercussions.
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