pH question

Joe31415 · Apr 9, 2021

I have all my corals in a QT designated specifically for corals (fish in another QT, DT still empty). I've been closely monitoring all the parameters and while everything seems fine, I've yet to see my pH move above 7.98 and usually closer to 7.5 or 7.6. When weather allows it, I do keep the window in that room open and I've even had an airstone in the tank (AIO tank with the airstone stuck under a filter in the back chamber, no bubbles make it out of that chamber) with the pump sitting on the window sill in front of the open window. Still no movement of the pH. Is that something I should worry about? And, if so, how should I fix it?
My thought was to add a CO2 scrubber and have the air pump push through it to an airstone in the back of the tank, but I don't see anyone doing that. It seems like everyone that uses a scrubber, adds it inline with their protein skimmer, which I don't have on this tank (and don't think I need, at least not yet).
I have BRS Two-Part, so I could add Soda Ash, but I think my Alk is fine as is and don't want to mess with it if I don't need to.

As for my parameters: pH sits just under 8, measured with a Pinpoint probe. Amm and Nitrite are zero, Nitrate sits in the 5-10 range (Amm/nitrite/nitrate measured with an API kit). Alk 8.5, phosphate .05, Calcium 446, Mag 1440.

Currently in the tank is a Frogspawn, a "frammer", 2 cyphastrea frags and a zoa. One of the cyphastrea frags seems to be slowly either turning white or getting covered in white fuzz, I'm not entirely sure. I'm also starting to develop some sort of algae that came in on a frag, but so far appears to be under control.

arking_mark · Apr 9, 2021

Many reefers are successful with pH between 7.8 to 8.5.

In my opinion stability is a more critical factor.

pH will typically be higher when the lights are on and lower when off. Many people try to minimize these small swings.

How are you measuring pH?

Have you done a cup aeration test?

A skimmer or airstone can also drive down your pH if it is delivering higher CO2 air. So if you a dosing a high-pH alk product that is boosting your pH, a skimmer delivering usually higher CO2 house air will work to drive pH down.

Joe31415 · Apr 9, 2021

I'm checking pH with a pinpoint monitor. I glance at it a few times a day and it's always about the same. So far I haven't noticed any swings that seem directly related to day or night (or rather lights on/lights off).
I haven't done the cup aeration test, but if it makes a difference, I have put an airstone in the tank with the pump on the window sill with the window open (so, open window in room plus outside air being pumped into tank) with no noticeable difference in pH.

On an unrelated note, do I really need filters in this tank since it's just corals? The only reason I keep the sock filter in is to catch any rock dust that gets kicked up from time to time, but I have copepods in there now and they're getting caught in it as well. It also has a media basket that came with some GFO that I haven't used, some odd cotton balls that are slowly turning yellow and I have some seachem matrix in it that I can just toss in the bottom of the tank.

arking_mark · Apr 9, 2021

Joe31415 said:
I'm checking pH with a pinpoint monitor. I glance at it a few times a day and it's always about the same. So far I haven't noticed any swings that seem directly related to day or night (or rather lights on/lights off).
I haven't done the cup aeration test, but if it makes a difference, I have put an airstone in the tank with the pump on the window sill with the window open (so, open window in room plus outside air being pumped into tank) with no noticeable difference in pH.

On an unrelated note, do I really need filters in this tank since it's just corals? The only reason I keep the sock filter in is to catch any rock dust that gets kicked up from time to time, but I have copepods in there now and they're getting caught in it as well. It also has a media basket that came with some GFO that I haven't used, some odd cotton balls that are slowly turning yellow and I have some seachem matrix in it that I can just toss in the bottom of the tank.

I'd run the cup aeration test then. It will give you some insight into your pH. If your tank pH and cup pH are the same inside and outside then that is probably your normal pH. If your inside cup pH is higher than your tank, added tank aeration could increase your pH. If your outside cup aeration is higher than your tank, outside air could raise your pH. If you want to raise your pH above its natural equilibrium with the environment, you can use high-ph Alk supplements (this should be balanced with Ca) or use a CO2 scrubber.

However, unless you are trying to achieve a specific goal with your tank, or are having a specific issue, I'd just leave it.

For my tank, I have high CO2 in my house without the ability to pull in outside air. My natural equilibrium is 7.9ish. I was dropping to 7.8 at night and getting as high as 8.0 during the day. I went with Kalkwasser dosing to bump up my pH which resulted in higher pH, but larger swings as my continuos Kalk dosing would pause to mix. I also have my refugium on the reverse lighting schedule to counteract the night swings. In the end, my stability wasn't great so I added a Skimmer with CO2 scrubber to help stabilize my pH. With this setup, I am actually able to dial-in a pH and tightly control it.

Tuning a Skimmer / CO2 Scrubber for pH Control

On my reefing journey, I found Kalkwasse + Skimmer + CO2 Scrubber to be very effective for bringing my pH from 7.8 - 7.9 to 8.26 - 8.36. I guess most people would just leave it at that. However, I wanted to be more efficient with the CO2 scrubbing material so I wanted to implement a...

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