How does auto. pH tester work?

[fishmonkey]

ok so i saw in a fish magazine about how you can use a ph tester to measure the co2 going into your tank and keep it from overdosing it or something. how can it do that? would it be worth getting one if i got a co2 tank?

[mgamer20o0]

worth it? its up to you i dont use them. the co2 regulator with a Solenoid turns on and off the co2 to keep it at the level you want.

[An t-iasg]

The pH probe in the aquarium keeps track of the pH of the water. The pH controller turns the solenoid on the regulator on and off according to the pH value you set on the controller. If you have the controller set at 6.8, the controller will turn the solenoid on, releasing the CO2, when the pH of the water rises above 6.8 and turning it off when the pH of 6.8 is reached again.

I have a pH controller and I like this system. It's not absolutely necessary but it does keep your pH pretty constant. It also saves CO2 since it only turns on when the pH rises. The CO2 isn't running constantly. I had a 5 lb. canister on a 10 gallon tank and it lasted for about a year and a half. The downside is that the controller system is rather expensive.

[Dzanda]

Originally Posted by fishmonkey

ok so i saw in a fish magazine about how you can use a ph tester to measure the co2 going into your tank and keep it from overdosing it or something. how can it do that? would it be worth getting one if i got a co2 tank?

Please ignore this if the other answers addressed your question, since it is a bit more technical than you may want.

You asked how a pH controller can control CO2, and that's actually a pretty good question! Here's a quick and dirty explanation:

pH is a measure of how acidic or alkaline something is (actually, the measurement depends on the ratio between hydrogen and hydroxyl ions, but there's no need to get that technical!). So, a pH controller measures (you guessed it) the pH of the aquarium's water. For our purposes, you can think of it as measuring how acidic the water is.

A pH of 7 is neutral, meaning that the water is neither acidic nor alkaline (basic), while a pH less than 7 means the water is acidic (with lower numbers being more acidic), and numbers greater than 7 indicate that the water is alkaline (with higher numbers being more alkaline). Because the pH scale is logarithmic, the difference between adjacent numbers (say 6 and 7) actually represents a 10 fold difference in acidity; this is why aquarists tend to care about smaller changes in pH (say 6.2-6.4).

But you're probably wondering what CO2 (carbon dioxide) has to do with pH, and that's the crucial part of this. When CO2 is mixed in water, one of the results is acid. So dissolving CO2 in water makes the water more acid, and thus lowers the pH. As plants use up the CO2 dissolved in the water, the water becomes less acidic, and the ph rises.

So, the idea is that you set the pH controller so that it turns the CO2 off and on for the desired pH. The end result is that by controlling the pH, one is also controlling the CO2 levels.

It's actually a bit more complicated, because the CO2 levels in the water depend on the pH, but that's a bit much for this post. Besides, I haven't figured it all out for myself, yet!

I hope this was helpful, and not too techie!

[fishmonkey]

wow that actually really helped

[Dzanda]

Glad to be of assistance!