Effect of pH change on alkalinity

[themcfreak]

Hey all. Probably answered, but quick search didn't find. I know that dosing soda ash can increase the pH of a tank, and increase the alkalinity of a tank. Sodium Bicarb increases the alkalinity, and is a slight decrease to pH.

Is there any effect to alkalinity if I raise pH another manner (say, a CO2 scrubber?) I changed the media in my scrubber, and the pH range went from 7.9-8.2 to 8.1-8.4. Does this have any effect on alkalinity.

The reason I ask that is I am struggling to keep my alk up. I am dosing around 40ml in my 100 gallons, and it still drops. In contrast, I am dosing about 14 ml of calcium, which is staying very steady. I considered I may be overdosing, but I (possibly ignorantly) would expect calcium to be dropping in addition to alkalinity if I was precipitating? None of my swings are huge (0.3 alkalinity over 24 hours usually), but it just seems strange that it drops, even though I am dosing so much more alk (and have increased the incremental dose too).

TIA

 

[nereefpat]

Increasing the pH will theoretically make corals and coralline algae consume alk faster. They combine alk and Ca by increasing pH, so in a higher pH environment, the combination is less delta...if that makes sense. That could be part of what you are seeing.

Now, about the apparent difference in Ca vs alk dosing: 0.3 alk consumption would only equate to about 2 ppm Ca consumption, which is impossible to detect on our kits. It is also common for those starting to dose to only have to dose alk. Part of that is the ratio mentioned above, and part of that is any water changes can keep up with Ca consumption better than alk comsumption.

 

[themcfreak]

And I do automatic water changes, using Tropic Marin Pro, so some 'dosing' occurs naturally that way. Is it becoming pretty standard that 2 part is not so equal in dosing anymore? I keep seeing more and more data seem to point to that not being the case anymore.

 

[themcfreak]

And, FWIW, I dose using Trident controlled dosing method. So the dose can and does fluctuate. The calcium is staying steady, the alk dosing keeps flexing up to raise alkalinity. End goal would be I get to a steady point, and then it just maintains.

 

[Randy Holmes-Farley]

Hey all. Probably answered, but quick search didn't find. I know that dosing soda ash can increase the pH of a tank, and increase the alkalinity of a tank. Sodium Bicarb increases the alkalinity, and is a slight decrease to pH.

Is there any effect to alkalinity if I raise pH another manner (say, a CO2 scrubber?) I changed the media in my scrubber, and the pH range went from 7.9-8.2 to 8.1-8.4. Does this have any effect on alkalinity.

The reason I ask that is I am struggling to keep my alk up. I am dosing around 40ml in my 100 gallons, and it still drops. In contrast, I am dosing about 14 ml of calcium, which is staying very steady. I considered I may be overdosing, but I (possibly ignorantly) would expect calcium to be dropping in addition to alkalinity if I was precipitating? None of my swings are huge (0.3 alkalinity over 24 hours usually), but it just seems strange that it drops, even though I am dosing so much more alk (and have increased the incremental dose too).

TIA

No, altering CO2 in any fashion (up or down) has no effect on alkalinity.

As noted above, it can impact formation of calcium carbonate as an ongoing process, but not directly on alkalinity.

 

[themcfreak]

Thank you very much!

 

[Randy Holmes-Farley]

You're welcome.

Happy reefing.