Which calcium type to use?

[Scrubber_steve]

Calcium Chloride Dihydrate CaCl2.2H2O

or

Calcium chloride Anhydrous CaCl2

 

[Scrubber_steve]

Dihydrate is less pure than anhydrous so it would be less expensive, but I wonder if there is any significant differences in how they interact with other elements when added to the water?

 

[C.Eymann]

The difference is presence of water in the dihydrate vs anhydrous, their bioavailability are the same, one is just more concentrated then the other. One thing you need to watch out for is contaminates, where ever you source it, might be wise to conferr with a fellow reefer has had success with said source, stateside here, Prestone driveway heat (anhydrous) is/or was back when DIY two part was coming onto the scene, dowflake (dihydrate) was another source, both were widely used with success, you simply needed more dow flake than you would of the Prestone due to its decreased potency due to presence of more water.
Basically what I'm saying is without sending a sample into a lab you don't really know if a source is safe until the so called "canaries" have tried it with their reefs.

 

[Scrubber_steve]

Purity values can usually be found with some research eg

http://www.calciumchloride.co.uk/calcium_chloride_grades.html

 

[C.Eymann]

Purity values can usually be found with some research eg

http://www.calciumchloride.co.uk/calcium_chloride_grades.html

That only tells you how much calcium chloride is in each, doesn't tell you if potentially harmful elements can be found in them. I remember when people were using dowflake there was a concern of bromide accumulating in a tank that doesn't see regular w/c where as I guess Prestone driveway heat didn't seem to have elevated levels of it to be a concern.
Just be careful, if one says 94% CaCl2, sure the majority of the remaining 6% is mostly water, but it's possible there can be traces of elements that could be harmful to a reef.

Just my .02

 

[sde1500]

Always intrigues me. I am so careful to use RODI water to prevent anything other than pure water in my tank. We always talk about that, controlling what goes in the tank. But if you are DIY dosing, 100% can't control what goes in, can't guarantee there isn't some small bit of something bad for the tank in the ice melt, or baking soda, or Epsom salts. Unlikely there will be, but can't be sure.

 

[C.Eymann]

Always intrigues me. I am so careful to use RODI water to prevent anything other than pure water in my tank. We always talk about that, controlling what goes in the tank. But if you are DIY dosing, 100% can't control what goes in, can't guarantee there isn't some small bit of something bad for the tank in the ice melt, or baking soda, or Epsom salts. Unlikely there will be, but can't be sure.

+1 I don't worry too much about baking soda and Epsom, they are made for human consumption so I hope their is some some control there, but Ice melt is made for driveway and sidewalk consumption. So yeah, not so much restriction as to what impurities are allowed or not.
Only reason I used Prestone back in the day is because dozens of other reefers were using it with no ill effects, however if the only choice I had was some similar CaCl2 product but different name/producer that I had never heard of someone using for a reef, I would stay away.
I don't want my reef to be a canary.

 

[Scrubber_steve]

Cannot b sure bought products are pure anymore than what i kight purchase from a Lab supply