Neptune Probe and Salifert test disagree on pH

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Let me start by saying that I'm not chasing numbers. I'm not making any drastic changes, but I do want to work from the best information I can get. My tank has been up for 2 years, I do a 15% WC every week and have never had pH issues.

Yesterday, I updated the AOS for my ApexEL. A few hours later, things went wonky - my pH was constantly moving. Dropping, raising, repeat, within minutes. I received about 80 notifications (going under 7.8 and then back over) over the course of about 4 or 5 hours. So I decided to recalibrate my pH probe. I was able to do that, with some help from Neptune. I did the manual calibration and it settled on 726 and 1036. Then retesting the calibration fluid gave me 10.0 and 7.01 so it seemed about perfect. In the tank, it said 7.88 at that point (normally my tank would fluctuate between 7.8 and 8.2 every day ).

That was low for that time of day (should have been at least 8.1) so I got out my salifert test kit and it read 8.15 (or thereabouts):
1624970101977.png
This is a pretty big difference in pH, so I got out a dip strip from our pool. That's not very specific of a test, so my options were 7.8 and 8.4. I would say it was in the 7.8 range which agreed with the Apex.

I knew that overnight the pH would drop further so I got out my old skimmer and popped it in the tank for aeration, hoping it would help. It didn't really seem to. Overnight, the pH dropped as normal and this morning the Apex reads 7.66. I have never seen my tank below 7.8 so this is a bit concerning for me. I tested with Salifert again this morning and it reads about 8.0. Another pool dip test and it looks around the 7.6 to 7.8 range.
1624970582712.png

So, I've come to the conclusion that my tank has probably been running at a lower pH than I thought. It's hot here right now, and the tank is running warmer (80ish), but even with Apex (which has always tested lower than Salifert) it has never dropped below 7.8 before (or at least not often). What should I be looking for in my tank? None of the fish are stressed. I did lose my BTA recently, and he had been declining for a while. My RFA is happy and healthy and my corals grow well (though I've lost color in some zoas, perhaps due to too intense of lighting, not sure). I have a mystic sunset monti that is a prolific grower. Other happy inhabitants are a ton of zoas, galaxea, chalice (doing well except where the galaxea is killing it...sigh), favites, war coral, duncan, candy cane, ricordea, lepto. The only coral not doing super well is an acan lord. I also have a fair amount of snails and hermits, a skunk cleaner shrimp, a fire shrimp, a Halloween urchin, a conch, and a strawberry crab, all doing very well.

So, thoughts? Suggestions? Is there a better back up test kit than Salifert I should pick up? Changes I should make to help keep my pH above 7.8? My alkalinity (tested last night at midnight LOL) is 9.0. I dose Red Sea liquid alkalinity daily, currently at 7.0 ml over 7 doses from 9 am to 11 pm. My lights are on from around 12:30 PM to 11:30 PM and I run a fuge (that has lots of oxygen bubbles in it) with the light from 11 PM to 8 AM daily.
 
Zoanthids

tjohnson3

Valuable Member
View Badges
Joined
Feb 28, 2021
Messages
1,097
Reaction score
1,044
Review score
+0 /0 /-0
Location
Tomball, TX
I’m starting to seriously doubt the Apex. I’ve seen a few posts where people are looking for help for something, posting their water params, and their ph is always low, and guess what… they’ve got an Apex! I’ve been having the exact same issue. Recalibrate… low ph… recalibrate… low ph… but EVERY other test (salifert, api, etc) has my ph above 8 while apex keeps telling me it’s under 7.5. This has been happening for 2 months straight… so if my ph was REALLY that low, I’m sure my tank would be dead… which is not the case. I’m following along to see what others have to say
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
I’m starting to seriously doubt the Apex. I’ve seen a few posts where people are looking for help for something, posting their water params, and their ph is always low, and guess what… they’ve got an Apex! I’ve been having the exact same issue. Recalibrate… low ph… recalibrate… low ph… but EVERY other test (salifert, api, etc) has my ph above 8 while apex keeps telling me it’s under 7.5. This has been happening for 2 months straight… so if my ph was REALLY that low, I’m sure my tank would be dead… which is not the case. I’m following along to see what others have to say
Randy is the expert and I've been reading his posts. He definitely says the meters, properly calibrated, are more accurate than the reagent tests. I mean, it's reading my calibration fluids spot on so....
 

tjohnson3

Valuable Member
View Badges
Joined
Feb 28, 2021
Messages
1,097
Reaction score
1,044
Review score
+0 /0 /-0
Location
Tomball, TX
Randy is the expert and I've been reading his posts. He definitely says the meters, properly calibrated, are more accurate than the reagent tests. I mean, it's reading my calibration fluids spot on so....
It reads my calibration fluids spot on, too… just not my tank apparently lol
 

srobertb

Active Member
View Badges
Joined
Jun 16, 2021
Messages
314
Reaction score
397
Review score
+0 /0 /-0
Location
SE Texas
Let me start by saying that I'm not chasing numbers. I'm not making any drastic changes, but I do want to work from the best information I can get. My tank has been up for 2 years, I do a 15% WC every week and have never had pH issues.

Yesterday, I updated the AOS for my ApexEL. A few hours later, things went wonky - my pH was constantly moving. Dropping, raising, repeat, within minutes. I received about 80 notifications (going under 7.8 and then back over) over the course of about 4 or 5 hours. So I decided to recalibrate my pH probe. I was able to do that, with some help from Neptune. I did the manual calibration and it settled on 726 and 1036. Then retesting the calibration fluid gave me 10.0 and 7.01 so it seemed about perfect. In the tank, it said 7.88 at that point (normally my tank would fluctuate between 7.8 and 8.2 every day ).

That was low for that time of day (should have been at least 8.1) so I got out my salifert test kit and it read 8.15 (or thereabouts):
1624970101977.png
This is a pretty big difference in pH, so I got out a dip strip from our pool. That's not very specific of a test, so my options were 7.8 and 8.4. I would say it was in the 7.8 range which agreed with the Apex.

I knew that overnight the pH would drop further so I got out my old skimmer and popped it in the tank for aeration, hoping it would help. It didn't really seem to. Overnight, the pH dropped as normal and this morning the Apex reads 7.66. I have never seen my tank below 7.8 so this is a bit concerning for me. I tested with Salifert again this morning and it reads about 8.0. Another pool dip test and it looks around the 7.6 to 7.8 range.
1624970582712.png

So, I've come to the conclusion that my tank has probably been running at a lower pH than I thought. It's hot here right now, and the tank is running warmer (80ish), but even with Apex (which has always tested lower than Salifert) it has never dropped below 7.8 before (or at least not often). What should I be looking for in my tank? None of the fish are stressed. I did lose my BTA recently, and he had been declining for a while. My RFA is happy and healthy and my corals grow well (though I've lost color in some zoas, perhaps due to too intense of lighting, not sure). I have a mystic sunset monti that is a prolific grower. Other happy inhabitants are a ton of zoas, galaxea, chalice (doing well except where the galaxea is killing it...sigh), favites, war coral, duncan, candy cane, ricordea, lepto. The only coral not doing super well is an acan lord. I also have a fair amount of snails and hermits, a skunk cleaner shrimp, a fire shrimp, a Halloween urchin, a conch, and a strawberry crab, all doing very well.

So, thoughts? Suggestions? Is there a better back up test kit than Salifert I should pick up? Changes I should make to help keep my pH above 7.8? My alkalinity (tested last night at midnight LOL) is 9.0. I dose Red Sea liquid alkalinity daily, currently at 7.0 ml over 7 doses from 9 am to 11 pm. My lights are on from around 12:30 PM to 11:30 PM and I run a fuge (that has lots of oxygen bubbles in it) with the light from 11 PM to 8 AM daily.
I have 2 Neptune PH probes (neither are actually the Neptune brand). One is older, the other one brand new. Both placeas far away from each other as possible. They were calibrated with different brand solutions. They both read within .1 one each other and often are within .02 of each other. They should be replaced yearly IMO.

They drift and fall off calibration over time. Mine drift down not up so if nothing else changes and my PH is dropping, I recalibrate first.

They need to be calibrated monthly or every few months.

I don’t need perfect PH readings. Knowing it’s “around 8.2” and falls “around 8.0” is enough data. I can see changes if I add a CO2 scrubber or increase algae growth. I need to be able to monitor and understand swings and be notified if they go above or below a range (I think mine are 7.5 and 9).

I don’t have time to test 5 points a day (including a midnight and 2am test) so while this may not be perfect, it is a really useful tool. It’s just not perfect.
 
Orphek OR3 reef aquarium LED lighting

blaxsun

Valuable Member
View Badges
Joined
Dec 15, 2020
Messages
1,670
Reaction score
1,614
Review score
+0 /0 /-0
Location
Saskatchewan
Have you tried enabling temperature compensation (TC) under the advanced tab for the PH probe? I found that it smoothed the numbers out somewhat for me and provided slightly more accurate readings. Note that if you enable this feature you have to update the Apex and recalibrate the PH probe.
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Have you tried enabling temperature compensation (TC) under the advanced tab for the PH probe? I found that it smoothed the numbers out somewhat for me and provided slightly more accurate readings.
I actually had to turn off the TC to get it to stop the constant flickering and alerting. Once I turned that off, it smoothed out and only alerted when it was legitimately low (without bouncing up and down every couple of minutes). When I did some reading and the temp would only change it around .01-.02, I decided I didn't need it (let me know if I got that wrong though, it was 1 am when I was reading about it LOL)
 

blaxsun

Valuable Member
View Badges
Joined
Dec 15, 2020
Messages
1,670
Reaction score
1,614
Review score
+0 /0 /-0
Location
Saskatchewan
I know you can set the TC value for the salinity probe, but I'm not sure what preset (hidden) TC value for the PH probe is. You're probably correct that it's not more than a few percentage points.

The default alarm range can be annoying at times, like when I inadvertently dumped some flakes and pellets into the tank while trying to remove the AFS drum and the PH proceeded to plummet for the next 8-12 hours... You might find that it's beneficial just tweaking the PH minimum value to something like 7.75, 7.70 (etc.) so that you don't get an excessive number of alarms.
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
I know you can set the TC value for the salinity probe, but I'm not sure what preset (hidden) TC value for the PH probe is. You're probably correct that it's not more than a few percentage points.

The default alarm range can be annoying at times, like when I inadvertently dumped some flakes and pellets into the tank while trying to remove the AFS drum and the PH proceeded to plummet for the next 8-12 hours... You might find that it's beneficial just tweaking the PH minimum value to something like 7.75, 7.70 (etc.) so that you don't get an excessive number of alarms.
Yeah, true. I wish they had perhaps more spaced out alerts or something, but it's been fine since I turned off the TC.
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Just spoke to someone at Neptune (I put a case in yesterday at the end of the day) and they were very helpful. They actually think the probe didn't calibrate properly. While in the app, I saw 10 on the 10.0 calibration fluid, the data recorded was 10.3 which he says is way too far off for a good calibration. I'm going to redo it, using his instructions, and thought I would include it here because it doesn't exactly match what I saw online:

1) Log in to Apex Local when doing this so you get real time readings from the probe. Going through the app or the website lags (which I have noticed) and that's likely why I thought my calibration matched the fluids but it really didn't.

2) When doing manual calibration, you only need it to be steady for about 20 seconds to determine it has 'settled'. I took online advice and waited much longer for it to settle (I went in 5 minute increments and if it changed in that 5 minutes, I did another 5. It took 20 minutes for the 7.0 and over 10 minutes for the 10.0 with this method). He didn't outright say it, but kind of implied that waiting that long could have caused calibration issues and that it's really not necessary.

So, I'll try it again this evening with this advice and see how it goes. I'll post updates to see if it improved any after that. He did say that if that doesn't fix it, to reply to my case and they'll see if they can come up with other ideas. As always, I had a very good interaction with their support staff (this is the second or third time I think).
 
Fritz

Pêcheur

Community Member
View Badges
Joined
Apr 17, 2021
Messages
85
Reaction score
65
Review score
+0 /0 /-0
Location
Baton Rouge
Just spoke to someone at Neptune (I put a case in yesterday at the end of the day) and they were very helpful. They actually think the probe didn't calibrate properly. While in the app, I saw 10 on the 10.0 calibration fluid, the data recorded was 10.3 which he says is way too far off for a good calibration. I'm going to redo it, using his instructions, and thought I would include it here because it doesn't exactly match what I saw online:

1) Log in to Apex Local when doing this so you get real time readings from the probe. Going through the app or the website lags (which I have noticed) and that's likely why I thought my calibration matched the fluids but it really didn't.

2) When doing manual calibration, you only need it to be steady for about 20 seconds to determine it has 'settled'. I took online advice and waited much longer for it to settle (I went in 5 minute increments and if it changed in that 5 minutes, I did another 5. It took 20 minutes for the 7.0 and over 10 minutes for the 10.0 with this method). He didn't outright say it, but kind of implied that waiting that long could have caused calibration issues and that it's really not necessary.

So, I'll try it again this evening with this advice and see how it goes. I'll post updates to see if it improved any after that. He did say that if that doesn't fix it, to reply to my case and they'll see if they can come up with other ideas. As always, I had a very good interaction with their support staff (this is the second or third time I think).
Yeah, when testing the probe in the calibration fluids, you want it as tight as possible to the 7.00 & 10.00.
10.3 is a significant departure from what it should read.
I would also recommend floating the fluid pouches in tank water before testing or calibrating the probe.
I retested my probe in the calibration solutions after my latest recalibration and got the following readings: 6.97/10.0
 

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
45,432
Reaction score
34,486
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
I retested my probe in the calibration solutions after my latest recalibration and got the following readings: 6.97/10.0

IMO, that's an important confirmatory step that few folks do.
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Yes, I clip the pouches to the divider in my biocube to get them up to tank temp. The first time I retested the pouches after calibration, the 10.0 read 10.0, but, it was likely because the app that I was using was lagging so I didn't see that it went to 10.3 until I looked at the graph later. It looks like the graph only captures every 10 minutes so it could miss this completely. I think the support person could actually see all the data points behind it, while I can only see what's on the graph.

Just redid the calibration using Apex local after TC was turned back on. Numbers settled much closer this time - 705 and 1001. Then retested the pouches and got 10.0 and 7.01 (10.0 was logged on the chart but the 7.01 was not for some reason). Then back in my tank and it improved slightly, but not significantly (7.79 before calibration and 7.82 after). After 5 minutes or so, put the probe back in 7.0 solution and got a solid 7.0. It's back in the tank now, and still adjusting, but currently at 7.81.

I did notice last time I calibrated (December) that it took several days at least for the probe to kind of stabilize and read where I thought it should. I can't really think of an explanation for that, but the pH increased consistently for several days until it stabilized.
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
I just looked up the last time I calibrated (February, not December like I thought) and I had a similar issue. It read low initially and the min/max crept up over several days. I posted on here about it too, so I have the chart:

1625002570752.png
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Well, still no good resolution here so I ordered a new BRS probe that should arrive tomorrow. I thought my probe was only a year old but noticed the manufacture date on it and it’s nearly 3 years old. It’s still odd that it didn’t start acting wonky until I updated the AOS but I find it very hard to believe that my tank pH decided to drop at the exact same time I did that update. I looked back through my logs to April and it is always steady and predictable. While I didn’t have the Apex last summer, my tank stats were stable then too for pH. Yes, it’s extra hot here this week but we always keep the house locked up tight and the air on, so that didn’t change either. Is it possible the probe wasn’t properly calibrated this whole time? I suppose so, but I still kind of doubt it.
Here’s my current chart and you can see exactly where I did the update.
A937E9F7-638E-4679-A82F-8726EB71FEF2.png
 
OP
hllb

hllb

Valuable Member
View Badges
Joined
Aug 30, 2019
Messages
1,698
Reaction score
1,233
Review score
+0 /0 /-0
Boy, this is really frustrating. This thing worked very well until I updated the AOS. This afternoon, the pH readings went haywire. Instead of increasing the longer the lights were on, it decreased, and then it would dip down, and shoot back up, and dip down again. It was crazy. I wasn't at home, but kept getting alerts. It would drop down to 7.2, go up to 7.5, drop back down...clearly something wrong, I mean, everything would be dead. So I get home and do a manual test. I get 8.2ish on both Salifert and API. Probe reads 7.37. Clearly big issues. I tested the 7.0 and 10.0 fluids I had saved and the 7.0 read about 7.1 and the 10.0 read about 7.9 LOL. The BRS probe arrived while I was gone, so I get that hooked up and try to calibrate. I have calibrated it 5 times now. The first 3 times didn't really work. The last two seemed to, but it's still reading my tank really low.

It currently reads 7.76, and a manual Salifert test reads Between 8 and 8.1 and API reads 8.0. Sigh...I don't really know where to go with this. Neptune offered to set up a troubleshooting appointment so I'll do that next week. But man, this is frustrating. I wish I never would have updated the AOS.
 

blasterman

Valuable Member
View Badges
Joined
Feb 14, 2019
Messages
1,730
Reaction score
1,923
Review score
+0 /0 /-0
I feel your pain. Ive gone through 3 meters the past year of various brands and they all require constant calibration and re calibration with fluid. This isnt exactly a category of instrumentation I'm impressed with.
 

Bruce60

Active Member
View Badges
Joined
Oct 28, 2018
Messages
189
Reaction score
241
Review score
+0 /0 /-0
Location
Bloomsburg, PA
I have also had some issues with the pH probes. If they start getting wonky you might want to inspect them, as sometimes there are deposits or growth on the probes that can impact performance. I clean them with RO/DI water and gentle wiping and recalibrate. Usually that works well, but occasionally after this process the probe readings are clearly consistently low (confirmed with multiple different manual tests). I usually wait a few days and then try recalibrating again. I have suspected that those calibrations were off (likely due to human error of some type), but it might also be a result of my cleaning the probe.
I would not be too fast to run and buy a new probe. You know your tank is doing well and these readings are obviously off. Trying a few recalibrations are inexpensive and might just work in the end.
 
BRS

Do you house a "Reef Safe" Angelfish in your reef tank?

  • YES and it's going good

    Votes: 90 41.7%
  • YES but it's not working out

    Votes: 6 2.8%
  • NO I have tried it in the past and it didn't work out

    Votes: 20 9.3%
  • NO I haven't tried yet

    Votes: 94 43.5%
  • Other (please explain)

    Votes: 6 2.8%
RED SEA
Top