Low pH - problem identified but help needed

[ReefingFun]

I've been having a low pH reading for the past 3 days now -7.6 to 7.7 - and identified the problem by process of elimination.
I believe the pH is low due to not enough aeration in the apartment. Considering it's really cold here I can't just open a window for most of the day.
Now I read about hooking up a tube to the skimmer and pump in fresh air like that is an option, but again that would require me to open the window a bit.

So anyone has any ideas how to solve this? Perhaps can explain how I go about the skimmer idea or perhaps other ways?


About the aquarium:

RSM 250
livestock: 1 yellow tang, 1 peppermint shrimp, 2 crabs, snails, 1 BTA, 1 Hammer coral

Readings:

Ca: 430-450
Mg: 930 (dosing this atm as waterchanges don't seem to help)
KH: 8-10 dKH
Salinity: 1021

Dosing Kh/Mg/Ca once week to keep up with consumption rate. For some reason my water changes don't really seem to add too much Ca & Mg


Thanks in advance

 

[reefer gladness]

Your pH problem is most likely related to the Mg deficiency and the imbalance that's going to cause. Your test results look off, it's unusual for calcium to be that high with salinity so low and your magnesium should be roughly 3x the value of your calcium test. ie. if you test 450 with calcium your magnesium should be around 1350ppm.

Not sure what kind of salt you're using but I would increase salinity to at least around 1.023 with a series of waterchanges and then dose magnesium daily as necessary to bring it up. Make sure you're using quality test kits as well. The range of alk readings between 8-10dKH is too wide, it should be stable. If your test kits are just that low in resolution get some Salifert test kits.

 

[PSU4ME]

I'd bring your salinity to 1.025/26 over a few changes. Lots of time co2 drops your ph so aerating with a skimmer is good bit if you keep your alk/ca in good ranges it will come in line.

Stability is better than perfection though. A swing of 3 tenths is acceptable...... Anything past that is too much

 

[ReefingFun]

I actually use SaLifert for Ca and Mg, but am really not happy with them and probably gonna change to Red Sea. When I test Mg I do 5 tests. 3 out of 5 readings are very different, fluctuating over 300 difference. It is not a reading error either.
I'm doing water changes every day and raising the salinity slowly, so that should be solved soon.

How does Mg influence pH btw? I read all the articles by Holmey-Farley about reef chemistry and didn't see any reference that Mg influences pH.

Your pH problem is most likely related to the Mg deficiency and the imbalance that's going to cause. Your test results look off, it's unusual for calcium to be that high with salinity so low and your magnesium should be roughly 3x the value of your calcium test. ie. if you test 450 with calcium your magnesium should be around 1350ppm.

Not sure what kind of salt you're using but I would increase salinity to at least around 1.023 with a series of waterchanges and then dose magnesium daily as necessary to bring it up. Make sure you're using quality test kits as well. The range of alk readings between 8-10dKH is too wide, it should be stable. If your test kits are just that low in resolution get some Salifert test kits.

 

[reefer gladness]

Mg doesn't influence pH directly but it does indirectly through the effects of calcium carbonate on pH. Here's a decent read on the relationship between Mg, Calcium and Alk A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com. Possibly the same one you've read already but there is an indirect relationship between Mg and pH. Regardless, I wouldn't screw around with anything else until the chemistry is in balance.

Something definitely amiss with your Mg testing, maybe you just got a bad batch. The Mg test has a resolution of 30ppm and I don't see a variance of more than 30ppm when testing more than once. Same with the Alk and calcium test kits, I never see the readings vary by more than 1 increment on the chart.

 

[steved13]

I tried running tubing from outside into the skimmer, it helped very little, about .1 increase. You don't have to open the windows all day, but if you can change the air in the room a couple of times per day that will help greatly. Also, make sure you have plenty of surface turbulence, for gas exchange, and keep the fans running.

 

[ReefingFun]

Alright I'll start dosing Mg daily and raise my salinity slowly and see what affect that has on my pH then.

Thanks for the helps guys!

 

[SantaMonica]

Any type of photosynthesis (from corals, macros) will bring pH up, so longer lighting hours will help.

Any decaying waste, or over feeding, or any feeding at all actually, will bring pH down, so limiting feeding will help.