Balancing pH, Alk/Ca, and Mg

arking_mark

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I keep reading @Randy Holmes-Farley articles and feel like I'm getting closer to understanding some reef chemistry.

As I've been dialing in my tank parameters and chasing some numbers, I'm wondering if there is a balance to strike for each tank and approach.

So I'd like to focus on my tank and where the numbers should be stabilized around.

So far, I've really focused on getting my pH stable. With my setup, I can dial-in pH and maintain it within .05. I've been targeting 8.35, but have started to get clumping sand due to abiotic precipitation.

This got me thinking that if I have a higher pH such as 8.35, I should be targeting a lower dKH to avoid some of this abiotic precipitation.

Since my tank is only 5 months old with a few frags, I was targeting higher numbers for increased growth. BRS had a nice little experiment with raised parameters that showed greatly increased growth.

So maybe the right combo is not pushing up all your parameters. Higher pH with lower Alk/Ca/Mag and lower pH tanks with higher Alk/Ca/Mag.

I was also thinking about equipment failure. If my Skimmer + CO2 Scrubber + Kalk fails, I'll be taking my tank from 8.35 to 7.9 pretty quickly.

So what combo would work best for my current situation?

pH: 8.25
Alk: 7.5
Ca: 450
Mag: 1400

This would give me slightly higher parameters than NSW and hopefully increased growth.

The one thing my tank has struggled with is getting Alk stability...which is what I've been ocusing on since achieving pH stability.

With what I theorized as mostly abiotic demand, just when I think I have it figured out it doesn't behave as expected.
 
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mdb_talon

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So maybe the right combo is not pushing up all your parameters. Higher pH with lower Alk/Ca/Mag and lower pH tanks with higher Alk/Ca/Mag.

The problem with high PH and low alk is that is a hard thing to achieve. Alk level is one of the two factors in how high your PH.

Personally i target a specific dkh and try to keep that stable. Then keep calc and MG in a reasonable range, but otherwise not especially concerned with them.

Then i do my best to keep PH high and stable. Reverse lit refugium to help stability. Outside air line to help keep it higher(my family breathes way too much).
 
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arking_mark

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The problem with high PH and low alk is that is a hard thing to achieve. Alk level is one of the two factors in how high your PH.

Personally i target a specific dkh and try to keep that stable. Then keep calc and MG in a reasonable range, but otherwise not especially concerned with them.

Then i do my best to keep PH high and stable. Reverse lit refugium to help stability. Outside air line to help keep it higher(my family breathes way too much).

My understanding of pH and Alk is a little different...and probably incorrect.

pH effects the carbonate and bicarbonate equilibrium in a tank. Which in turn buffers the tank from pH changes.

However, the air CO2 is really the driving factor. Anything you add to the tank to increase or decrease will be temporary as the tank equalizes with the air.

So a constant Kalk drip is adding Hydroxide to the tank which adds alkalinity as it interacts with the tank CO2. Let it sit, and the pH will come down...but I don't believe you lose any alkalinity.

So in my tank, I have things that are constantly reducing the tank CO2 to achieve steady pH (Kalk drip, Skimmer with CO2 scrubber, refugium on reverse lighting schedule).

With the exception of the Kalk, nothing adds Alk to the tank. In fact, I can up my alk and keep my pH the same with boosting alk supplements beyond my tank demand. Just add a little baking soda.

One of the issues I have is that without elevated pH, my Alk/Ca demand is quite low...and I need to reduce kalk dosing.
 
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arking_mark

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So here is what I think is happening...


I believe Magnesium will allow one to keep Alk/Ca at higher levels without is precipitating out.
 

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