Low ph, when rest of chemistry is "ok"

[brentlee6969]

A question I have been trying to find the answer to myself but I am having no luck. My ph tends to stay between 7.65 and 7.8. I check my alk nightly and it is normally 10.4 dkh to 10.6 dkh. I currently run a c02 scrubber on my skimmer and it has been changed less than a week ago yet it doesn't raise ph much. What are my other options? I've tried kalk but it doesn't give me higher ph without raising alk and calcium to much.

 

[mdb_talon]

My best guess is faulty ph reading if your alk is that high and ph that low and using a scrubber.

Having said that inadequate aeration can also cause low ph(however in a high co2 environment more aeration can actually decrease ph but i doubt your co2 is that high).

I would do the test of aerating water sample outside then check the ph. If it is still that low then that points to bad ph readings.

 

[brentlee6969]

My best guess is faulty ph reading if your alk is that high and ph that low and using a scrubber.

Having said that inadequate aeration can also cause low ph(however in a high co2 environment more aeration can actually decrease ph but i doubt your co2 is that high).

I would do the test of aerating water sample outside then check the ph. If it is still that low then that points to bad ph readings.

I have it checked on my hanna meter and my ph probe and they are within .1 of ea other

 

[mdb_talon]

I have it checked on my hanna meter and my ph probe and they are within .1 of ea other

If you are convinced it is correct(and your alk is correct) then the only answer is quite high co2 tank levels. Unless your home co2 levels are extremely high you should at least be able to get it up a bit by increasing aeration of the tank.

 

[brentlee6969]

The only time I have seen it higher(in the 8.2 range) I was running kalk in the ato. I stopped running it however because my consumption was not high enough for what it added. At a lower dose I didn't get the high ph. My only other thought to possibly correct the issue is a refugium. Does that seem plausible?

 

[bnord]

my situation is not unlike yours, and continuing to add data points, including a new CO2 monitor (reading 507 tank side with no one watching)
My Alk is 10.5-11 and I aerate the return chamber, plenty'o surface warbling - Milwaukee (calibrated high and low) consistently reads in the late evening 7.8 -7.9. Hanna consistently 8.2 to 8.3.
Want to believe the Hanna, but I haven't calibrated it.
Tank grows LPS VERY well and SPS in very inconsistent, with some slow to rapid death in some frags.
So don't know that I have low pH holding me back as much. as I believe I. could do better, if I could get it higher

 

[mdb_talon]

The only time I have seen it higher(in the 8.2 range) I was running kalk in the ato. I stopped running it however because my consumption was not high enough for what it added. At a lower dose I didn't get the high ph. My only other thought to possibly correct the issue is a refugium. Does that seem plausible?

It can definetely have a large impact if you have macroalgae growing fast. It does release some co2 when lights are off but not so much as it consumes. For that reason though many people run it with lights on reverse cycle of the tank. It would boost your ph some and stabilize the swings.

Again though they key is having enough nutrients for it to grow well.

 

[brentlee6969]

my situation is not unlike yours, and continuing to add data points, including a new CO2 monitor (reading 507 tank side with no one watching)
My Alk is 10.5-11 and I aerate the return chamber, plenty'o surface warbling - Milwaukee (calibrated high and low) consistently reads in the late evening 7.8 -7.9. Hanna consistently 8.2 to 8.3.
Want to believe the Hanna, but I haven't calibrated it.
Tank grows LPS VERY well and SPS in very inconsistent, with some slow to rapid death in some frags.
So don't know that I have low pH holding me back as much. as I believe I. could do better, if I could get it higher

My readings stay close to ea other but I am just lost because between the skimmer with scrubber + surface agitation I would think I should be fine. My house has even been opened up more often since it is winter in Florida, so I would think the c02 levels would decrease in my house. Yet I don't notice any difference in my ph.

It can definetely have a large impact if you have macroalgae growing fast. It does release some co2 when lights are off but not so much as it consumes. For that reason though many people run it with lights on reverse cycle of the tank. It would boost your ph some and stabilize the swings.

Again though they key is having enough nutrients for it to grow well.

Appreciate the help I am off work tomorrow and may try to aerate a cup outside and also aerate one tankside.

 

[mdb_talon]

My readings stay close to ea other but I am just lost because between the skimmer with scrubber + surface agitation I would think I should be fine. My house has even been opened up more often since it is winter in Florida, so I would think the c02 levels would decrease in my house. Yet I don't notice any difference in my ph.

Appreciate the help I am off work tomorrow and may try to aerate a cup outside and also aerate one tankside.

No problem. I think the aeration tests always make sense as first step. Luckily there are not many direct factors of ph.....but unfortunately it still often not an easy "fix"

 

[brentlee6969]

No problem. I think the aeration tests always make sense as first step. Luckily there are not many direct factors of ph.....but unfortunately it still often not an easy "fix"

None of the fixs are that hard either I just want to know where the problem may lie.

 

[arking_mark]

With proper tank aeration, normal indoor CO2 (500ppm is good), and no pH lowering dosing, any pH measurement below 7.8 NBS is a measurement error.

Based on your numbers 500ppm CO2 and 10.5 dKH, your tank in equilibrium with the air will have a pH of roughly 8.3 NBS.

How I use a cup aeration test to help pinpoint certain pH issues.

• I do 2 tests. One outside and one next to the tank.
• I run an airstone for about 1 hour and measure pH.
• If the outdoor test isn't around 8.2 NBS, then I know I have a meter or Alk issue...and it's never an Alk issue.
• If the next to tank test is below 8.2 NBS, then I have higher indoor CO2...almost always the case.
• If the next to tank test is higher than the tank, I have an aeration issue or something else that is driving down pH...it's almost never something else unless I'm dosing something that lowers pH.
• If the next to tank test is lower than the tank but not at desired levels, then I need to look at my pH management setup.

 

[brentlee6969]

With proper tank aeration, normal indoor CO2 (500ppm is good), and no pH lowering dosing, any pH measurement below 7.8 NBS is a measurement error.

Based on your numbers 500ppm CO2 and 10.5 dKH, your tank in equilibrium with the air will have a pH of roughly 8.3 NBS.

How I use a cup aeration test to help pinpoint certain pH issues.

• I do 2 tests. One outside and one next to the tank.
• I run an airstone for about 1 hour and measure pH.
• If the outdoor test isn't around 8.2 NBS, then I know I have a meter or Alk issue...and it's never an Alk issue.
• If the next to tank test is below 8.2 NBS, then I have higher indoor CO2...almost always the case.
• If the next to tank test is higher than the tank, I have an aeration issue or something else that is driving down pH...it's almost never something else unless I'm dosing something that lowers pH.
• If the next to tank test is lower than the tank but not at desired levels, then I need to look at my pH management setup.

Thanks for the advice. I'm gonna do this tomorrow.

 

[arking_mark]

Thanks for the advice. I'm gonna do this tomorrow.

Good luck!

 

[brentlee6969]

Just checked tank ph with hanna checker it shows 7.6. Ph probe in the sump shows 7.56. I have 2 cups, 1 inside and 1 outside with air stones in them now.

 

[Mical]

I'm curious about your other parameters - SG, Cal & magnesium...

 

[arking_mark]

Just checked tank ph with hanna checker it shows 7.6. Ph probe in the sump shows 7.56. I have 2 cups, 1 inside and 1 outside with air stones in them now.

Can't wait to see the results

 

[SlugSnorter]

List of params would help, that test will also help show the issue.

Beyond that, you use RODI water in your tank, and are not currently dosing anything right?

 

[brentlee6969]

Tested all at the same time.
Tank - 7.8
Next to tank - 7.8
Outside - 8.6

 

[brentlee6969]

List of params would help, that test will also help show the issue.

Beyond that, you use RODI water in your tank, and are not currently dosing anything right?

Rodi water and currently dosing N0pox just to drop nitrates a bit and red sea alk supplement.

 

[Randy Holmes-Farley]

Tested all at the same time.
Tank - 7.8
Next to tank - 7.8
Outside - 8.6

Those are pH after aeration?

Outside is not likely that thigh in reality, but it does show that indoor air is high in CO2.