Low pH, what else can I try?

Exoticpets · Oct 12, 2020

Hello everyone, I have a 40 gal (total) AIO that has been running for around 6 months, I transferred it from a smaller tank with existing media, water, rocks, etc.
We have had low pH since the beginning but we didn't want to chase numbers. (averaging 7.9-8.0). The other parameters are stabilizing but pH has started to drop drastically (as low as 7.5 averaging 7.7). My corals are starting to die and I out of ideas of the cause that's causing it.

Last parameters check (none others checked):
Temperature: 77.3 F
Salinity: 1.023 SG
pH: 7.9
Ammonia: 0.25 (always this result, using API)
Nitrite: 0
Nitrate: 15
Calcium: 460 (dosed after this)
Phosphate: 0
Alkalinity: 10
Magnesium: 1230

Things I have tried:
Buffer in RO top off water to keep at 8.3 and above
Buffer in tank to raise (it drops quickly)
CO2 scrubber
Leaving a near by window brings it up to 8.1-8.2
Added gyro/wave maker to increase flow and surface agitation (also have an additional flow)

Is there anything else I can do or what may be causing this to happen? Thanks for any insight you may have.

40g Nano · Oct 12, 2020

Have you done a combo like a fan AND the buffer

mindme · Oct 12, 2020

Leaving a near by window brings it up to 8.1-8.2

Doesn't sound like surface agitation is the issue then. But it also hints that it needs more oxygen and that the Co2 levels near the tank are high doesn't it?

Maybe another source to oxygenate it with the use of another Co2 scrubber?

Not a big fan of buffers. Temporary fix at best.

chipmunkofdoom2 · Oct 12, 2020

I would discontinue using the buffers. A buffer is just an alkalinity supplement that boosts pH. As you have seen, the pH boost fades while the alkalinity doesn't. High pH alkalinity additives play a part in the battle against low pH, but using buffers is a really expensive way to dose alkalinity and boost pH.

Unless improperly implemented, a CO2 scrubber should have fixed your issue. It's possible your home has incredibly high CO2 that would exhaust a CO2 scrubber quickly, but it should have at least fixed pH temporarily. Did you notice an increase when the CO2 scrubber was installed?

Exoticpets · Oct 16, 2020

14g Nano said:
Have you done a combo like a fan AND the buffer

I think this actually did it! I have set up the scrubber and we would also open the window but did not buffer to get it up there. I added the buffer on Tuesday Wednesday the pH was all over but Thursday it seems to stabilized. Hopefully it will hold because like mindme and chipmonkofdoom2 said I hate using buffers!
in the past it would have dropped back down by now so maybe it needed a push to stay up
Thank you everyone for your help!

Exoticpets · Oct 21, 2020

update. pH is still swinging. We have the scrubber set up still cause it seems to keep it above 7.5. Any ideas?

Bobblehead · Oct 21, 2020

When I was dosing Kalkwasser only, my pH was around 8-8.2. Since I started 2 part using sodium carbonate in addition to Kalk, my pH has gone up to a steady 8.4.

OSU · Oct 22, 2020

You could try pumping outside air into your skimmer. I also would check and make sure your pH probe is calibrated and working correctly. 7.5 is really low for an alkalinity of 10.

Strad12 · Oct 22, 2020

The name of the game is to reduce CO2 levels in your water. Try Kalkwasser instead of a buffer in your ATO. Consider switching to a Soda Ash based alkalinity supplement (assuming you dose your tank daily). This combined with Kalkwasser will hopefully give your pH a boost. If high CO2 in the surrounding air is the root cause, then more surface agitation will make it more difficult to remove excess CO2. You could also look to implement a refugium on an opposite lighting schedule from your display. Algae will absorb CO2 and release O2 into the water at night, limiting a daily swing that might be causing stress. A powerful light on your refugium will make the algae grow quickly, thus having a larger effect on CO2 levels and therefore your pH. If you have a skimmer, implementing a CO2 scrubber should be more effective than piping in outside air.

I'm having the same issue on my nano, so this has been my course of action. I tried a CO2 scrubber with limited success. pH increased by .1, but that could have been a testing error. The pH of my tank swings from around 7.7 to 8.0 daily, and thats with soda ash dosing. I'm going to install a refugium tomorrow and try out Kalkwasser next week. I'll let you know if any of these prove to be especially successful. I'm hoping the refugium and Kalkwasser combined can keep it up around 8.3-8.4.

Exoticpets · Oct 24, 2020

Thank you everyone for your suggestions, I will need to look more into Kalkwasser, is this something that only goes into the ATO water or tank as well?
My magnesium has dropped below 1300 recently so I am working to bring that back up. My LFS recommended trying to get it 1450+ to see if it helps pull the pH up but either way I'm dosing to at least 1350.
I also brought some water up the the LFS to be tested (just to confirm I'm reading the test correctly) and they matched up with what I have.
I actually lowered the surface agitation (there's still some) when I added the CO2 scrubber, it seemed to work better, is this the correct thing to do?

Strad12 · Oct 24, 2020

Regarding the CO2 scrubber, if the problem is that there's high CO2 in the surrounding air dissolving into your water through contact with the air, then less surface agitation means a lower surface area where undesirable gas exchange can happen. Combine this with the Co2 scrubber, where pure O2 and N2 are coming in and CO2 is leaving, and you will be exporting more CO2 than is entering the system. If it helped, keep it up! I think Kalkwasser is going to make the biggest difference in your system. The CO2 scrubber and refugium have had little if any impact on mine, unfortunately.

Exoticpets · Oct 29, 2020

Update!!! I have been able to get my pH consistent and my corals are starting to look better. Its been a week so I'm cautiously excited.
Apparently if you dose calcium and alkalinity, but not magnesium, it can cause pH to drop unproportionally to the others.
My mag was in the safe range but on the lower end and I noticed it was low just before my scheduled water changes (I tested after water changes).
I pulled the mag up and its now dropped a very small amount but in proportion with the alk.
pH has been 8.0-8.1 over night and 8.1-8.2 during the day!

Hincapiej4 · Nov 26, 2020

Beautiful!

Yates273 · Nov 26, 2020

I’m jealous of you. I’m glad you figured it out. I’m having issues with low ph also. I do not dose Magnesium since mine is already high. I am at a loss as what to do.

Exoticpets · Nov 26, 2020

Jason Yahr said:
I’m jealous of you. I’m glad you figured it out. I’m having issues with low ph also. I do not dose Magnesium since mine is already high. I am at a loss as what to do.

The C02 scrubber made the biggest difference for me after I got the other parameters balanced.
what are you parameters?