Short term pH increasing?

[TheStrangler]

Hi there, so I've currently been trying to slowly battle the day/night pH changes that come from not having a reverse cycle refugium. I just setup an algae scrubber which I'll keep on a reverse cycle, but I'm looking to make a short term change because things are going in the opposite direction of intended. My daytime pH was previously about 8.2 and it'd drop to 7.8 on a regular cycle at night before rising back up. Its been inching downwards, touching 7.5 at night. While I wait for algae to build up in my scrubber, is using baking soda an acceptable additive? I'd mix it in with fresh RODI water and add it bit by bit into my sump.

Over the past week, my alkalinity has been pretty stable in the 8.5-8.6 range and I've been slowly increasing it just with 3-4 gallon water changes using Instant Ocean salt which should have a much higher alk. Calcium at 470 +- 10ppm for the past week, and magnesium at 1350 +- 10ppm.

 

[mdb_talon]

First question would be have you recently calibrated your probe? Assuming you have and want to increase PH that means increasing alk, lowering co2, or both.

Something like baking soda will increase alk and ph some, but your alk is in a good range now so increasing it with goal of increasing ph in my opinion would not make sense unless you really want alk higher.

My guess is you really need better gas exchange or the room co2 levels are high so leading to high co2 in tank.

 

[Garf]

Dosing a little Kalkwasser at night will increase pH but as above, you can only put in as much as your Alkalinity consumption will allow, unless you wanna raise it a bit, obviously.
First job is to double check your readings.

 

[TheStrangler]

Thanks, yeah I do expect my Alk will raise a little bit just naturally as I changed salt mixes, I'm just doing that pretty gradually. I'm not too concerned about raising it up as long as its gradual. Air exchange is probably a concern at night, but I've kept the window open for a 24 hour period to see the effect and it didn't appreciably effect the pH. Maybe raised it by 0.05 but its still too low. My probe is properly calibrated and is pretty consistent with a salifert pH test as well. Even if I factor in a margin of error, I'm still far too low at night. I've got surface agitation in the display tank, a protein skimmer and algae scrubber in the sump which should all be helping with gas exchange.

 

[arking_mark]

Thanks, yeah I do expect my Alk will raise a little bit just naturally as I changed salt mixes, I'm just doing that pretty gradually. I'm not too concerned about raising it up as long as its gradual. Air exchange is probably a concern at night, but I've kept the window open for a 24 hour period to see the effect and it didn't appreciably effect the pH. Maybe raised it by 0.05 but its still too low. My probe is properly calibrated and is pretty consistent with a salifert pH test as well. Even if I factor in a margin of error, I'm still far too low at night. I've got surface agitation in the display tank, a protein skimmer and algae scrubber in the sump which should all be helping with gas exchange.

Just an observation. If low pH is due to air CO2 (most are), then your skimmer is working against anything you do as it's doing a fantastic job aerating with that in house higher CO2 air.

If you want to slow down that nighttime pH drop, you can turn off your skimmer.

If you want the skimmer to.help raise your pH, it needs to pull in outside air or CO2 scrubbed air.

 

[TheStrangler]

Just an observation. If low pH is due to air CO2 (most are), then your skimmer is working against anything you do as it's doing a fantastic job aerating with that in house higher CO2 air.

If you want to slow down that nighttime pH drop, you can turn off your skimmer.

If you want the skimmer to.help raise your pH, it needs to pull in outside air or CO2 scrubbed air.

Thanks for the tip, I'll give that a shot. My doors and windows are open during the daytime but its still too chilly at night to do that. Just putting my skimmer on a reverse cycle might work perfectly.

 

[arking_mark]

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...

www.reef2reef.com