Why Don't More People Control / Lower Ph Via Co2?

Rynofasho · Jul 20, 2011

So I'm looking to go the CO2 route soon and in researching, found that it is easy to manipulate (namely, lower) your pH using CO2 as it forms an acid in the water. This really opens a lot of possibilities to me in keeping fish as my tap water is traditionally very hard.

Whenever you look for ways to lower pH though, everyone always says either RO or your SOL besides the obvious other small things like driftwood, blackwater, etc.

Why don't more people use CO2 to control pH?

StandbySetting · Jul 20, 2011

Because CO2 is expensive and very unstable in water, as soon as it gasses off the pH increases again. The best way to decrease the pH is to add peat and bog wood.

Rynofasho · Jul 20, 2011

Well if you have a planted tank that is always running CO2 and you are effectively diffusing it, I don't see it being unstable at all. Even more, people use them with pH controllers hooked to a solenoid so that it will keep your pH within a desired range.

Vin Swords · Jul 20, 2011

too much work...

RadaR · Jul 20, 2011

Rynofasho said:
Well if you have a planted tank that is always running CO2 and you are effectively diffusing it, I don't see it being unstable at all. Even more, people use them with pH controllers hooked to a solenoid so that it will keep your pH within a desired range.

It really doesnt.
the pH probe is assuming that any change in pH is solely down to carbonic acid. However as we all know, there are many other variables in water that can alter the pH. Therefore, pH units attached to CO2 systems tend to exaggerate on the amount of CO2 in the tank and it shuts it off because it thinks the CO2 is getting too high. Plants don't get the CO2 they need because instead of the CO2 being 40ppm (like the pH probe thought), it could actually be 15ppm. I guess it would keep your fish safe, just not your plants. Unhealthy plants though will decay and lead to fish deaths.

TwoTankAmin · Jul 20, 2011

It really doesnt.

Actually in response to the OP's question, it really does. When it comes to making water more acid it doesn't matter where the pH lowering comes from, co2 or the so called "other variables". So if you want to drop your tank say from a normal 8.0 pH out of the tap to 6.5, hook up the co2 and the pH controller, set it for 6.5 and off you go. All you need to worry about is that the amount of co2 needed to get the pH to that level isn't also harmful or fatal to your fish. This has nothing to do with plants or their co2 needs which is another issue entirely.

The true downside to this method of lowering pH is if the power goes out, the co2 will stop and then the pH will move up. Moreover, any problems with the co2 system that cause it to stop working, including forgetting to refill the bottle will also have negative consequences.

RO water is a much more effective way to manage lowering and holding pH stable at lower levels and the same applies for lowering TDS. That is because soft water and acid water are not the same thing. The first related to conductivity and TDS while the second relates to pH. And yes I know that normally high pH and high hardness go together and low pH and soft water do as well, but not all the time.

Mikaila31 · Jul 20, 2011

It does but it also depends on your water. If you have a high buffering capacity nothing is going to work except RO water. You can inject co2 but eventually you reach a level where you have to let off due to risk to livestock. If your buffering capacity is really high you might only drop pH slightly. If buffering capacity is low the same amount of CO2 could cause a pH crash on a tank. If your water is very hard, I'm betting it has a high buffering capacity. RO water reduces this which is key to changing pH.

I use pressurized CO2, but its just time controlled. Sure it might change pH a little bit, but its main purpose is for the plants. RO water would be a much cheaper option then CO2 if you are really worried about pH. Unless your pH is crazy high then you rarely need to even worry about it.