Trying to lower alkalinity while maintaining calcium

[Scott.h]

For some reason lately I'm having a hard time getting my calcium from 400 to 420. I'm assuming it's having something to do with trying to lower my kh or the kind of calcium I'm using. I'm vodka dosing so my goal has been keeping a kh of 8. I'm not adding any alkalinity at all UNLESS it's being added by my cal (I'm finding no info on what's in it) , and I'm lightly dosing hydrocloratic acid with water changes. Note, Everything is fine in my tank, but I'm trying to understand this none the less. I'm also trying to keep all my supplements in the same brand line.

I'm running tropic Marin reef pro salt at 1025, dosing seachem magnesium to 1350, keeping kh at 8.5.. Struggling to balance that at 8, and finally dosing seachem reef calcium at 400. It seems like whether I add the calcium or not it stays right at 400. Also I have, but don't use the seachem Kalkwasser because I'm happy with my pH at The current (and stable) 8.2, and I don't want to raise my alkalinity, which Kalk does. I was thinking about switching my calciums to the Seachem powder reef advantage calcium, but that has pH buffers in it and magnesium. I would rather dose individually so I know exactly what I'm getting rather then a blend.

So I'm confused as why I can't seem to go from 400 to 420 with my calcium levels. Would anybody have any insight on this?

 

[Randy Holmes-Farley Verified Community Expert]

Seachem Reef Calcium does add alkalinity, and is also carbon dosing, so it is likely the worst choice for your situation.

Try any brand of calcium chloride.

 

[Scott.h]

Ok, duly noted. I was originally under the impression that the seachem reef calcium was calcium carbonate, but I haven't found any verification of what it is.. even on seachems website. Using calcium carbonate do I need to keep the calcium higher then 400, or is it just causing precipitation?

How does the carbon dosing come into play with this? Switching to calcium carbonate as my only supplement source eliminates this as a problem?

 

[Randy Holmes-Farley Verified Community Expert]

Calcium chloride, not calcium carbonate. Calcium chloride will boost only calcium and not alkalinity.

Seachem Reef Calcium is calcium polygluconate. If and when the polygluconate part is metabolized by bacteria, the result is alkalinity and driving of some bacterial growth. Some of it may be removed in other ways, such as by skimming. Seachem apparently does not understand the alkalinity aspect of the product, despite my pointing it out to them in one of their forums (where they did agree that some was metabolized, IIRC).

Unfortunately, it is not easy to know how much alk you get from it since it depends on what portion of the polygluconate is fully metabolized, and what portion is removed while still a negatively charged organic molecule. For that reason, I generally do not recommend this product.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, the Seachem Reef Advantage calcium would be OK if you like Seachem products. The amount of everything except calcium chloride is small, and there is no buffer in it.

 

[Randy Holmes-Farley Verified Community Expert]

Ok, duly noted. I was originally under the impression that the seachem reef calcium was calcium carbonate, but I haven't found any verification of what it is.. even on seachems website. Using calcium carbonate do I need to keep the calcium higher then 400, or is it just causing precipitation?

How does the carbon dosing come into play with this? Switching to calcium carbonate as my only supplement source eliminates this as a problem?

I'd aim for about 420 ppm calcium, but the exact value is not typically very important.

 

[Scott.h]

Calcium chloride, not calcium carbonate. Calcium chloride will boost only calcium and not alkalinity.

Seachem Reef Calcium is calcium polygluconate. If and when the polygluconate part is metabolized by bacteria, the result is alkalinity and driving of some bacterial growth. Some of it may be removed in other ways, such as by skimming. Seachem apparently does not understand the alkalinity aspect of the product, despite my pointing it out to them in one of their forums (where they did agree that some was metabolized, IIRC).

Unfortunately, it is not easy to know how much alk you get from it since it depends on what portion of the polygluconate is fully metabolized, and what portion is removed while still a negatively charged organic molecule. For that reason, I generally do not recommend this product.

Jeesh ok, I would have never figured that one out. I'll switch immediately. So is there a specific reason chemically why a calcium chloride level would elevate higher then calcium carbonate?

By the way, after getting into the hobby a bit ago trying to understand various things, and all my googling, I always seem to end up on one of your written articles getting (free) information and explanations that I couldn't seem to find otherwise. So I just wanted to say thank you. You've helped me out far beyond this, and probably single handedly kept my stuff alive.

 

[Randy Holmes-Farley Verified Community Expert]

Calcium carbonate is the same material as live rock, and is not soluble in tank water, so does not provide either calcium or alkalinity.

Thanks, I'm glad you found the articles helpful.