Don't mean to jump in on someone else's thread but when you guys talk about a pH controller, does it basically just monitor your pH and start and stop your CO2 as necessary to keep your pH in a specific range?
And if I am reading @Greggz
correctly you have your controller on a timer as well? If the job of the controller is to keep your pH within a certain range, why not let the controller run 24x7? Or is the premise that regardless of the pH increase, you do not ever want your CO2 coming on at night?
I assume that this is the same reason you run an airstone for a few hours each night, to get rid of CO2 and raise the pH? What is the benefit in doing so?
Yes a pH controller turns your CO2 solenoid on and off. For instance, with mine my low point is set at pH 5.50. So when the pH drops to 5.50 it turns the CO2 off. When pH rises back to 5.60 it turns CO2 back on. So my pH drifts between those two levels during the CO2 injection period.
You will hear lots of pros and cons of CO2 controllers. Personally I wouldn't be without one. Makes it easy to make accurate small adjustments and less worry about CO2 in general. Dialing in CO2 by counting bubbles or adjusting flow rates is tricky business, and takes a lot of effort to fine tune. If I want to drop pH by an additional 0.05 to see what happens, I just adjust the setting. Couldn't be easier.
And not insignificant is that it acts as a fail safe to protect the fish.
I do not run CO2 overnight, as plants are not using it then. Most folks run their CO2 this way, as plants are only using it during the lighting period.
I run the air stones (strong air pump!) only for a few hours each night. When lights go off I like to degas tank quickly and create lots of O2 for the comfort of the Rainbows. It also creates a lot of flow which moves fish waste/detritus across the substrate to the rear of the tank.
I really don't know if it helps the plants or not, but have always been of the mind that good O2 levels can only be a good thing.