PH Controller question

[crazycanuck]

Hello,

I am new to the board but am a long time hobbyist. I am fairly new to keeping fish in the Ottawa area however, and the water parameters from the tap are very different from the well water I grew up with back in Manitoba!

I recently purchased an Ista PH controller and am having some issues with having it turn off the solenoid on my CO2 regulator. I calibrated the controller as per instructions I found on youtube, and it is reading the PH properly. I set my desired PH to 6.9, and my aquarium water prior to installing the CO2 system was about 7.2 PH with the usual low KH (ca. 2 KH) that is found in Ottawa tap water. I opened the needle valve to start diffusing CO2 and since I am new to CO2 injection I am only doing about one bubble every two to three seconds. I monitored the PH as it dropped due to CO2 concentration, and it hit 6.9 and kept falling. At about 6.69 PH I unplugged the solenoid from the controller out of fear that it would keep dropping further. I assumed that the PH controller would shut off the solenoid after it dropped slightly below the 6.9 setting, but it did do so.

Has anybody ever used one of the Ista controllers? If so, any suggestions on what I might be doing wrong? There is also the "hi" and "lo" setting on the controller, but I can't find anything on the internet in terms of instructions for the unit (I believe it is a Taiwanese product) and the youtube videos I have found do not clearly indicate what Hi or Lo actually does. So I am thinking that perhaps my issues might have something to do with my lack of understanding of this feature of the unit, but who knows!

Any information would be greatly appreciated!

[lucius]

The Youtube video I found says that if you are keeping planted tanks, it should be set to high but doesn't really say why.

I would let the controller keep going.  I don't think it would necessarily shut down at 6.69 because it probably stays on a bit longer to ensure that the value you set gets reached and stays set.

[crazycanuck]

Thanks for replying, it ended up being a faulty unit. Got it replaced and the new one is working perfectly!