Chemistry imbalance?

[SCReef'n]

So for some time I have been using Sodium Hydroxide, BRS calcium and BRS Mag. I do semi-regular water changes once a week of 10%. I control the hydroxide dosing based on my pH set to come on at a pH of 8.3 and off at 8.5. This wa working well for several months and managed my Alk at 8-10 dkh. However recently I have noticed my Alk dropping as the average pH in the tank stays high enough not to dose as much hydroxide to meet my Alk demands. So I have started to supplement my Alk using sodium carbonate along with the they hydroxide to compensate along with the same BRS cal and Mag. Now I find my hydroxide rarely comes on. Maybe once a week for <5 minutes as my pH is rarely lower than 8.3. This has resulted in a gradual transition from primarily using hydroxide to primarily using carbonate as the source of Alk in my tank. My question is should I be doing something different? I have not been using any sort of “part c” for ionic balance. I have been seeing a significant tissue necrosis issue on my acropora and I’m worried I have created some sort of imbalance. Icp tests show everything is within the “normal” ranges.

 

[Randy Holmes-Farley Verified Community Expert]

So for some time I have been using Sodium Hydroxide, BRS calcium and BRS Mag. I do semi-regular water changes once a week of 10%. I control the hydroxide dosing based on my pH set to come on at a pH of 8.3 and off at 8.5. This wa working well for several months and managed my Alk at 8-10 dkh. However recently I have noticed my Alk dropping as the average pH in the tank stays high enough not to dose as much hydroxide to meet my Alk demands. So I have started to supplement my Alk using sodium carbonate along with the they hydroxide to compensate along with the same BRS cal and Mag. Now I find my hydroxide rarely comes on. Maybe once a week for <5 minutes as my pH is rarely lower than 8.3. This has resulted in a gradual transition from primarily using hydroxide to primarily using carbonate as the source of Alk in my tank. My question is should I be doing something different? I have not been using any sort of “part c” for ionic balance. I have been seeing a significant tissue necrosis issue on my acropora and I’m worried I have created some sort of imbalance. Icp tests show everything is within the “normal” ranges.

What you are doing seems fine, although it can be hard to know if it is a real tank effect on pH or a drifting pH meter. I'd at least recalibrate to see if it is the latter.

It is useful to dose Balling Part C, but there's not likely an effect from not doing so that is causing the pH to slowly decline. Water changes partly offset the need for Part C, but I'd use it.

 

[SCReef'n]

It is useful to dose Balling Part C, but there's not likely an effect from not doing so that is causing the pH to slowly decline.

Ph is has increased over time vs decreased. But I’ll calibrate the probe all the same. Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Ph is has increased over time vs decreased. But I’ll calibrate the probe all the same. Thanks

Sorry, yes, that was a typo. I meant increased. It could happen for real reasons due to external influences (e.g., CO2 level in the room), or due to more photosynthesis in the tank (e.g., growing corals or algae), or to calibration drift.

 

[SCReef'n]

How do I figure the amount of part c to use?

 

[Randy Holmes-Farley Verified Community Expert]

How do I figure the amount of part c to use?

https://www.reef2reef.com/threads/diy-three-part-with-balling-part-c-recipe.1063575/

 

[SCReef'n]

Sorry how much of the solution do I dose? And I’m not quite sure of the purpose of part c if I’m using mag from brs. Which is in theory primarily mag sulfate

 

[Randy Holmes-Farley Verified Community Expert]

Sorry how much of the solution do I dose? And I’m not quite sure of the purpose of part c if I’m using mag from brs. Which is in theory primarily mag sulfate

I'm not sure I understand the confusion since Miami lays it all out, but let's start with exactly how much alk you are dosing now, and what recipes those two are.

 

[SCReef'n]

Sorry for being slow I’m just not getting it. Currently dosing
Sodium carbonate - baked baking soda. 100 ml/day
Sodium hydroxide - small amount to maintain ph
Brs calcium carbonate - 150 ml/ day
Brs mag.- as needed to maintain ~1350-1400 ppm

 

[SCReef'n]

I do see the 1:1:1 ratio now sorry

 

[Randy Holmes-Farley Verified Community Expert]

Not a problem. I'd use that 1;1;1 ratio based on the total alk needed, and tweak the calcium up or down as needed.

I'd use the MAG recipe at a much reduced ratio from what you have been down to the 5.4% mentioned in the article. I would not base it on magnesium testing, although one can do that.