Understanding Ca,Mg,Kh,...

[Alfrareef]

Hi guys,

Following my learning for SW aquariums, last month I've taken the doser step following FM balling light.
After 2 weeks with the minimum dosing and some experiences I feel the need to understand better the relation between the components dosing and the overall impact in the water. Ex: why Ca and Kh and going up and Mg is going down and what's the adequate procedure.

I'm sure this should have been a hot topic at R2R, even if I couldn't find a systematic source, so I appreciate if you could give me some directions or point me to some posts/articles where I can get more knowledge.

TIA.
AR

 

[Reefing Madness]

@Randy Holmes-Farley

 

[Alfrareef]

Googled it and found very interesting stuff. Already inside part 2 which was exactly what I was looking for.

Thanks to Mr. Holmes-Farley for sharing so extensive work. Some questions already answered and new question already to address. After study and if needed I'll return.

For the ones with same need try:
http://reefkeeping.com/issues/author/rhf.php


As per you guys sorry and honestly I'm new at this forum and I was expecting a more structured help, but I guess you prefer solving those problems like if my cat peed 250ml over the aquarium should I use carbon for 3 days or some PH buffer...

Rgds,
AR

 

[Randy Holmes-Farley Verified Community Expert]

How much did magnesium drop? If more than 1-2 ppm per day, the result is testing error, and not real (or possibly due to a water change or changes in salinity).

 

[Alfrareef]

Thanks for your time and information.
The magnesium dropped 20 mg/l=ppm (my JBL test resolution) over 3 days. I'll buy a new test (different brand) and cross check until understand better the basics for water chemistry. Any recommendation?

 

[Randy Holmes-Farley Verified Community Expert]

That 20 ppm is almost certainly below the reproducibility of the kit.

 

[Alfrareef]

My thought (and my issue) also. I'll test with a different kit trying to understand the trend and drop rate. Thanks for the support.

 

[Alfrareef]

Hi Randy,

In a article you've wrote for Advance Aquarist, Aquarium Chemistry: Magnesium In Reef Aquaria, October 2003

"After the solid calcium carbonate has appeared in the system by whatever means, precipitation of CaCO3 will begin immediately. What processes inhibit continued precipitation of CaCO3 onto a growing crystal? The main thing happening in normal seawater is likely the impact of magnesium (though phosphate and organics may play an important role in some aquaria).24 This is the point that magnesium gets onto the growing surface of the crystal, essentially poisoning it for further precipitation of calcium carbonate. Since magnesium can reduce the likelihood or extent of calcium carbonate precipitation in this fashion, it thus acts to make it easier to maintain high levels of calcium and alkalinity."

At certain point you mention that phosphates and organics may play an important role in some aquaria, in a way related with CaCO3 precipitation inhibition.
Since I'm still learning about this and i've not taken a chemistry degree i'm having difficulties understanding this.
Can you please elaborate a little more about it and explain what could be that role and impacts?

TIA,
AR

 

[Randy Holmes-Farley Verified Community Expert]

At certain point you mention that phosphates and organics may play an important role in some aquaria, in a way related with CaCO3 precipitation inhibition.
Since I'm still learning about this and i've not taken a chemistry degree i'm having difficulties understanding this.
Can you please elaborate a little more about it and explain what could be that role and impacts?

Sure. Both organics (at least some organics) and phosphate get onto the growing surface of calcium carbonate crystals and "poison" them against further calcium carbonate precipitation, just as magnesium does (shown mechanistically in detail in the article below, phosphate and organics would behave mechanistically similarly).

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2006-06/rhf/index.php

I tested this myself for other reasons (wanting to boost coral growth) by putting polyacrylic acid ( a fairly nontoxic and negatively charged synthetic polymer) in seawater and found I could greatly supersaturate the seawater with calcium and alkalinity relative to the same seawater without the polymer, before precipitation started. So clearly, such organics can reduce precipitation.

FWIW, the effects of these two may be all or part of the reason that raw artificial seawater may not be able to hold elevated calcium and alkalinity as well as reef tank water.

 

[Alfrareef]

Thanks Randy for the easy to understand explanation!
I suppose we can say that if the Phosphates its increasing and the calc decreasing it's due to organisms calcium consumption and not precipitation. Is it so?

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy for the easy to understand explanation!
I suppose we can say that if the Phosphates its increasing and the calc decreasing it's due to organisms calcium consumption and not precipitation. Is it so?

Alkalinity is the bellweather for calcium carbonate precipitation, whether by corals or abiotically. It responds much faster than calcium.

Phosphate would not rise due to precipitation, but it might decrease as some gets incorporated into the calcium carbonate.

 

[115lol]

I got the same question, thanks for the info

 

[Alfrareef]

Interesting... Alkalinity is the bellwether...
That's a good way for keep it simple. Now I need to review some concepts to finnaly understand what goes up and what goes down using those assumptions.
Thanks for your time.