Low PH or PH probe

[hilde123]

I have been chasing what I have thought to be a low PH problem in my tank for the last 6 months or so. The PH seems to be peaking at 7.9 to 7.95 and drops to 7.75 to 7.8 at night. I have tried many things, adding a large air pump drawing air from outdoors, piping skimmer inlet to fresh air, and dosing kalkwasser. Nothing seems to be working. I am measuring my PH from a probe connected to my aquacontroller III, it has two probes connected one to calc reactor and one to tank sump. I calibrate the tank probe once a month and it seems that each time I calibrate it, the measured PH in my tank drops more. The probe is a Pinpoint and is 1 year old. Each time I use my chemical test kit to check water chemistry, I notice that the ph reads quite a bit higher .2-.3. I have ignored this because reading off a kit is just how dark or light the color is which doesnt seem too accurate. I always thought my calibrated PH probe would be superior to the chemical tests. Today I used two different chemical test kits and each show the PH to be between 8.0 and 8.1 while my ph probe (calibrated 2 days ago) shows 7.75. Is there a reason these readings would differ so much? Does excess CO2 affect the probe and not chemical tests? Any experiences or ideas would be greatly appreciated. Thanks

[psteeleb]

I wouldn't consider the range you're getting a problem. But like you I would want to know what the true reading is. My test kits have always tested about 0.2 higher then my calibrated probe. This may be coincidence or it may be based on the test kit reading something more or less then the probe. I'm going to tag along to see if anyone else chimes in.

I will add; when I first set up my tank it ran 7.8 - 8.0. After a year and a half it ranges from 7.9 o 8.1. FYI, I use the DIY two part.

[hilde123]

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