errant pH readings ?

[gregzz4]

At what point do we, or I, start ignoring errant readings ?

Maybe more of these questions may show up, now that summer is over, and our home air quality goes down ...

The pH pen I bought boxing day crapped out. It won't cal anymore, so I tossed it. I was told it only holds a 6 month warranty wish I'd known that when I bought it
$60 down the drain - thanks Milwaukee

So, here's what I'm dealing with

My 4-month-old reef started off with a pH reading of 7.8 in the am and 8.2 before lights out. This is after a 12 hour light cycle

Now, in the morning, it starts off with very low pH readings ... sometimes as low as 7.5, according to my DA probe, which is plugged into an SL1

I've tried re-calibrating the probe a couple times, and have just bought a new Pinpoint probe, so I'll report tomorrow what I find, but my new cal readings are no better with the old DA probe
I'll spend the day tomorrow cal-ing the new Pinpoint probe, but I suspect it will not be any different

I say this as the new PPoint probe in my QT ( cal'ed and only 1 month old ) is giving me the same readings with cal solution as the suspect probe is .....

I find it hard to believe my pH could be as low as 7.49 when my Alk is 7.5 and my Ca is 420

My skimmer feed is running on outside air, our windows are still open to give fresh air, the furnace fan is still running, I open doors all day long ...

Something is off with my readings ....

As I said, I'll report tomorrow after I cal the new probe, but I don't feel it will make any difference as my QT Pinpoint probe gives me the same readings in cal solution ...


Any suggestions ???