pH probe drift

[raidendex]

I've never used a probe before for constant readings and for that matter rarely even measure pH with something like API test kits, but since I got the Apex set up about a week ago I now monitor pH (normal grade probe).

I've calibrated it in the 7 and 10 solutions, numbers seem to stabilize after about a minute in each if not faster, and then in it went.

Since it's been in the tank it started to slowly drift up from initial of 7.89ish to now up to 8.17.

So I am wondering if this is actual readings and my pH is slowly creeping up for some reason or is it possible that since the probe is new it's adjusting and will eventually stop at some point where I would calibrate it again.

Thanks!

 

[kurt_n]

Be aware that pH is not constant throughout the day. It will be the lowest just your lights are turning on and the highest when your lights turn off. That's perfectly normal. I see a 0.2-0.3 drift during the course of the day.

If that's not what you're seeing, and the pH continues to climb regardless of your lighting, then something isn't right with the probe.

 

[raidendex]

Right, it's not a fluctuation due to certain changes through out the day. And I actually have sump and display lights on somewhat opposite times to cut down on sways like that.

Here is the graph for the past few days, as you can see it's slowly creeping up. It is possible this is true, I've recently upgraded to 180g tank so may be things are adjusting in chemistry as well, and I do dose soda ash at about 25ml a day (which really should not affect pH in over 250g of water that much).

I just mainly want to find out if it's possible that pH probe is just drifting/adjusting for a first week of being in water or something

 

[kurt_n]

Just wanted to make sure you were aware of the pH cycle. I'm often surprised how many folks don't know about it.

I've never seen any of my pH probes (on my 3rd) take time to break in. ORP probes *definitely* take a good 3-5 days to stabilize, but I've never noticed a pH probe do that.

I was curious what my recent pH history looked like so I pulled it up. Looking at my 7-day pH history ( http://www.reeftronics.net/kurt-n/apex-history ), I can see a slow upward creep over the last 7 days. But looking over the last month, I don't see any up or down trend. Pretty sure my trends are due to overall CO2 levels in my house (except for the obvious day/night thing.) Maybe you're just seeing the same type of stuff? If it keeps rising over the course of a couple weeks, then I'd suspect a bad pH probe. But until you get more data, it just might be the normal swings for your tank.

 

[raidendex]

Yep, I'm not really worried was just wondering if probe could be doing that on it's own. I guess so far it seems like probe should not drift and those are the actual readings from the tank, which again does make certain sense since I've upgraded from 120 to this 180 last week and I'm sure lots of things are still trying to balance out.

 

[raidendex]

Looks like regular probe did drift during first few days.

Even though it's been showing normal swings since then, I just did a recalibration as well as added a BRB lab grade pH probe to the system both now back do to about 7.9. Right before calibration regular probe was showing around 8.2.

Will see how the two probes will behave now.

 

[gregr]

Sounds like you have it under control but for reference the pH in my tank goes down to right about 8.0 at night and up to about 8.2 during the day. That seems pretty standard for systems that have calcium reactors. So to me your numbers look good.

 

[raidendex]

That's not what I'm describing.

Average reading drifted up around 0.3 points after installing standard probe and then stayed there displaying expected behavior of going a bit down a bit up.

Re-calibrating it brought the average back down around 0.3.

So initially it seem to take some time for the regular pH probe to adjust, which is why I guess it is good to re-calibrate them a week after initial install.

Also here is the comparison of standard pH probe and BRB lab grade one. Both were calibrated yesterday and initially showed same readings initially, but withing 30 minutes drifted a part a bit.

Graphs look pretty close, just seems the reaction time differs a bit. Of course the readings a little different as well. But at least since profiles of the graphs are close they are working about the same.