What's the deal with Calcium Acetate?


Phish Lover
I usually dose just plain calcium chloride, either in a balanced formula or not, and then add the necessary sodium carbonate/bicarbonate. But I have seen some products that use calcium acetate along with the calcium chloride. Does this have any benefits?
Perhaps this article by Randy will help:

From this article:

"One-part balanced additive systems: Calcium Acetate

Calcium acetate is a product that has gotten relatively little publicity despite its apparent ease of use and the commercial availability to aquarists. In some ways it is similar to the combination of limewater and vinegar.16 When dissolved in water (fresh or salt), you have calcium ions and acetate ions. The acetate is rapidly metabolized by tank organisms to form bicarbonate, carbon dioxide, and water:

CH3COO- (acetate) + 2 O2 � HCO3- + CO2 + H2O

This equation suggests that pH of such tanks may stay near the low end of normal, because of the excess carbon dioxide, but the practical experience of people using calcium acetate suggests that this is not a big concern.

Calcium acetate may also facilitate the conversion of nitrate to nitrogen gas (N2)16 in anoxic regions of live sand and rock by providing the carbon source necessary for the process (but this has not been demonstrated one way or the other). The equation below shows the process that could take place:

5 CH3COO- (acetate) + 8 NO3- � 10 CO2 + 4 N2 + 13 OH- + H2O

One of the sources of calcium acetate to aquarists is Salifert�s All in One (a product that also contains some strontium, amino acids, and some trace elements). It is a liquid product that can be poured directly into a tank with no immediate concerns about pH. The current version of their commercial product is 250,000-mg/L calcium acetate, so it contains the equivalent of 3,160 meq/L of alkalinity. This products sells in the US for about $31.50/L. Consequently, it costs about $10.00 per thousand meq/L of alkalinity. That price makes it very expensive for a tank with a large demand for calcium and alkalinity, but the zero initial costs make it attractive for small tanks, especially nano-reef tanks.

I have no information on the purity of the material, or the exact nature of the �trace elements� in it. Everything in the bottle will be delivered to the tank. It poses no unusual safety concerns. The upper limit to how much calcium and alkalinity can be supplied to a tank in this fashion depends on two factors. If the metabolism of acetate is rapid and the dose is very high, oxygen might be depleted. If the conversion is slow then acetate can build up in the tank (not itself a significant concern except perhaps at very high levels where it might confound an alkalinity test2). Habib Sekha of Salifert has indicated that using the doses recommended on the bottle will not lead to either of these issues being problematic.

Overdosing is not expected to be an unusual problem, but if one makes significant additions in this fashion, the alkalinity will take time to show up completely in the tank because the acetate takes time to be metabolized. Consequently, I�d wait a day after adding it to measure alkalinity. Calcium measurement won�t be similarly impacted. Tank salinity will not increase over time using calcium acetate."