pH probe reading all over the place, always sinks

James77 · 07/25/2018, 11:36 AM

Setup is an AC Jr with a PM1 using a BulkReef Lab Grade probe. Probe is in sump with Finnex heater, Octopus DC skimmer, and Octopus DC Varios skimmer. Only other probes in water are temp probe for a Ranco and the Apex temp probe. Water parameters are dosed and read Alk 8.5, Calcium 425, and Mag about 1300. Open top tank so its pretty well oxygenated and house is far from airtight.

I set this up on my new tank last Friday. Initially, pH was reading steady 8-8.1 or so for about 48 hours, where it then gradually sank to 7.02, and held dead steady there for several hours.

I calibrated the probe again using 7 and 10 solutions. Once in tank water, it again started at about 8 and sunk to 7. I removed probe from sump and put in glass or tank water. It started around 8.2 and sank to 7.4 steady for several hours.

Around the time of the initial sinking, I had added a waster collector with shutoff relay(Octopus). I unplugged that (and with it the skimmer) this morning and pH reading spiked to low 8's initially, then sank again to where it is at now about 7.5

Is this a probe issue? A PM1 issue? If electrical interference, why would it run fine for a couple days then repeatedly plunge?

I am picking up a pH test kit this afternoon. I do have a torch coral, small anemone, and yellow tang in there and they look perfectly healthy no matter the reading.

EthanKyle · 07/25/2018, 07:59 PM

Is it a new probe?

Sent from my iPhone using Tapatalk Pro

kurt_n · 07/27/2018, 09:44 PM

Same question as EthanKyle... what's the history of that probe?

I usually run my pH probe until it's dead since it's more informational than anything else. And I've had a few die like you're describing, so at this point I'd lean towards the probe.

d0ughb0y · 07/27/2018, 10:24 PM

If you bought the ac jr with the old ph probe, then you need to get a new ph probe. Ph probes don’t last forever and the sign that it needs replacement is if it cannot hold it calibration like what you described.

James77 · 07/29/2018, 09:41 AM

Probe is just fine, the user I’m not too sure about though.

It’s a brand new.... ORP probe

In my defense of that silliness, it does not say ORP on it and it was listed as pH in Apex. It’s been over decade since I’ve used ORP and forgot they just look different than pH, I just thought the bulk reef brand pH was styled differently.

Thanks for replies though.

kurt_n · 07/30/2018, 11:35 PM

Those are always the easiest answers!

I've got pH and ORP probes located in the same area and I never remember which is which when I want to calibrate my pH and have to trace the wires. I get it!

07/25/2018, 11:36 AM	#1
James77 Registered Member Join Date: Aug 2005 Location: Rhode Island Posts: 8,158	pH probe reading all over the place, always sinks Setup is an AC Jr with a PM1 using a BulkReef Lab Grade probe. Probe is in sump with Finnex heater, Octopus DC skimmer, and Octopus DC Varios skimmer. Only other probes in water are temp probe for a Ranco and the Apex temp probe. Water parameters are dosed and read Alk 8.5, Calcium 425, and Mag about 1300. Open top tank so its pretty well oxygenated and house is far from airtight. I set this up on my new tank last Friday. Initially, pH was reading steady 8-8.1 or so for about 48 hours, where it then gradually sank to 7.02, and held dead steady there for several hours. I calibrated the probe again using 7 and 10 solutions. Once in tank water, it again started at about 8 and sunk to 7. I removed probe from sump and put in glass or tank water. It started around 8.2 and sank to 7.4 steady for several hours. Around the time of the initial sinking, I had added a waster collector with shutoff relay(Octopus). I unplugged that (and with it the skimmer) this morning and pH reading spiked to low 8's initially, then sank again to where it is at now about 7.5 Is this a probe issue? A PM1 issue? If electrical interference, why would it run fine for a couple days then repeatedly plunge? I am picking up a pH test kit this afternoon. I do have a torch coral, small anemone, and yellow tang in there and they look perfectly healthy no matter the reading. __________________ Jim Current Tank Info: 120g Mixed Reef and 75g Freshwater

07/29/2018, 09:41 AM	#5
James77 Registered Member Join Date: Aug 2005 Location: Rhode Island Posts: 8,158	Probe is just fine, the user I’m not too sure about though. It’s a brand new.... ORP probe In my defense of that silliness, it does not say ORP on it and it was listed as pH in Apex. It’s been over decade since I’ve used ORP and forgot they just look different than pH, I just thought the bulk reef brand pH was styled differently. Thanks for replies though. __________________ Jim Current Tank Info: 120g Mixed Reef and 75g Freshwater

07/25/2018, 07:59 PM	#2
EthanKyle Registered Member Join Date: Jun 2012 Location: La Verne, CA Posts: 163	Is it a new probe? Sent from my iPhone using Tapatalk Pro

07/27/2018, 09:44 PM	#3
kurt_n Registered Member Join Date: May 2006 Location: WA Posts: 2,592	Same question as EthanKyle... what's the history of that probe? I usually run my pH probe until it's dead since it's more informational than anything else. And I've had a few die like you're describing, so at this point I'd lean towards the probe.

07/27/2018, 10:24 PM	#4
d0ughb0y Registered Member Join Date: Mar 2008 Location: sf bay area Posts: 5,165	If you bought the ac jr with the old ph probe, then you need to get a new ph probe. Ph probes don’t last forever and the sign that it needs replacement is if it cannot hold it calibration like what you described.

07/30/2018, 11:35 PM	#6
kurt_n Registered Member Join Date: May 2006 Location: WA Posts: 2,592	Those are always the easiest answers! I've got pH and ORP probes located in the same area and I never remember which is which when I want to calibrate my pH and have to trace the wires. I get it!