CO2 with a monitor

[crashar]

Ok

I recently acquired a used CO2 regulator and tank (thanks Zima) and a CO2 monitor/controller (thanks audioslave_68) here in the classified section.  They are set up and seem to be working fine. 

My question is which is best? Should I run the CO2 and the controller on a timer to go off when the lights are off, or should I leave it on all the time and let the controller manage the CO2 levels during the dark periods?  I am currently leaning toward leaving it on constantly and in order to maintain stable PH levels.  Is this just wasting CO2?  Will I get dangerous swings in PH if I shut it off at night. 

I did a water change yesterday.  My normal pH without CO2 is stable around 7.4.  Is there an optimum pH range I should be looking for?  How much play room is safe?

I currently have 4 x 65w compact flourescent bulbs on a 90g.

Any help is appreciated.

Harold

[Jeff1192]

I have never used a CO2 controller so I dont' have much experience with that.

You definitely don't need to worry about pH swings. My CO2 runs on a timer, coming on a few hours before lights on and turning off about an hour before lights out. My pH swings well over a full point during the day (early morning it's 7.6-7.8 and by the end of the day it's down around 6.2, sometimes less).

I originally monitored my CO2 levels with a pH monitor but now I use a drop checker (much more reliable is you have the proper water in it, 4dKh). If you google drop checker you'll find lots of information about them.

In terms of how much CO2 you want here's a good link to check out.
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

I still much prefer the drop checker because it will be far more accurate but the above info is good as well.


Hope this helps some.

Jeff

[fischkopp]

The pH swing caused by CO2 injection isn't critical in most cases, because it's a slow change, not a matter of seconds. So you can switch of the CO2 at night without any problems. Biggest problem with CO2 and fish are too high CO2 concentrations (refer to chinese drop checker). So one thing to keep in mind: even though you have a controller, always make sure you are around to check on the fish if you play around with CO2 settings. 

Take a look at the images, that's whats happening to the pH in my planted tank every day. The CO2 is simply on a timer, a controller will even the CO2 saturation during the day. In my tank the pH is slowly falling during the day, which means that the CO2 injection is slightly higher than needed.

The drop checker as described by Jeff is the best way to monitor the CO2 saturation in the tank. The optimum is about 30pmm, which will decrease the pH by about 1 degree. So given the pH in your tank settles at 7.4 deg without CO2, you will be aiming at a pH of 6.4 or lower by the time the lights come on.

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[crashar]

Thanks for the info.  I am watching everything closely over the long weekend and everything looks fine so far.

H.