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Re: Aquatic Plants Digest V3 #28

>Date: Thu, 15 Jan 1998 15:00:49 -0800
>From: Stephen Pushak <teban at powersonic_bc.ca
>I think another approach would be to examine the pH changes which occur
>in a tank with continuous CO2 injection during the day versus those of a
>tank where the CO2 injection is stopped at night. 

I can't run such an experiment because all our tanks are on controllers. 

What about this for a alternative...

The pH controller turns off the CO2 when the pH has fallen to 6.95 and turns it 
on when the pH has risen to pH 7.05.  This corresponds to a change from 16.85 
mg/l to 13.40 mg/l at 5.0 dKH.  Knowing the exact water capacity of the tank and 
the time between the controller going off and on, I can determine how many 
milligrams of CO2 was used in that time period.  By tracking the controller 
cycling times over a period of a day, I can determine the difference in usage 
caused by photosynthesis.

>Why not measure directly what you want to know when that's simple? ;-)

If only it were ...

OK, can anyone think of a simple way to track the controller cycles?  I would 
need a computer (got one near the tank).  I can plug a 6v power supply (Discman 
power unit) into the controller so that I have 6v when it's on and 0v when it's 
off. The power supply could even control a relay to provide "open/closed" 
actions (kind of like joystick buttons...). I can program. What would be a good 
computer port to connect up to?  What would be the programming trick to sense 
the voltage or closure?  I used to have an old computer with MS-Basic that could 
do this in a flash.  Now I only have a sophisticated Pentium thing with either 
Visual C++ or Delphi. 

If you have some suggestions, send to booth at frii_com.