From a biological point of view, an uncharged (organic, Calcium Gluconate) molecule requires less energy be expended for a coral to absorb that molecule, and the coral can absorb multiple molecules of Calcium, as well as an easily metabolized carbohydrate, with less energy expended, than it would expend absorbing a single charged molecule (ionized, Calcium Chloride.) I have used Calcium Gluconate for a very long time. I am not going to feed you a bunch of anecdotal balderdash over it, though.
That said, if you have a serious calcium depletion, you should use an ionic calcium supplement, and Calcium Chloride seems to be Randy's preference. I would be careful about what I selected however, and would stick pretty close on an item by item checklist to the two products (Dow or ESV) that Randy recommends. These products contain Sodium Chloride, Magnesium Chloride, and Calcium Hydroxide, as well as Calcium Chloride.
Potassium Chloride... as far as the K (Kalium/Potassium) level in the tank, I would not dose for it unless there was a confirmed test showing that it was lacking... it can cause problems if dosed carelessly. So I would not use a Calcium Chloride "substitute" with Potassium Chloride in it. The "State" uses Potassium Chloride to stop the heart, during an execution by lethal injection, but it is a very large dose.
For maintaining, however, I would get away from multi-part solutions (Calcium, Alkalinity, and magnesium combined, including calcium reactors, and kalkwasswer, etc.) and hand dose individual 'parts,' something that my experience has shown, every hobbyist should know how to do, giving a very firm handle on the levels, although it is not as cheap as "bucket chemistry." I don't agree with Randy's methods, but he is not going to suggest something that will wipe out your tank.
