Epson salts and baking soda are just grocery store items.
Calcium Chloride is ice melter for winter driveways. It also is used to speed the hardening of concrete in winter. Redimix concrete places sell bags of it. Be sure to ask for calcium chloride not the brand name. One company here even had the anhydrous (compare to kent turbo calcium) form which is 94-97%. Brand name was cal-chlor (i think). A 25 pound bag was $8 or so. They asked me what I was using it for and then just gave me a bag at no charge.
Magnesium chloride is also an ice melter but much less common as it costs more. It is also used for dust control in roads and landscaping. But most landscaping firms here have a liquid form.
I found an industrial chemical supplier here that has both calcium chloride and magnesium chloride in 50 pound bags. They have to ship in the magnesium chloride but do not charge for that shipping. To them it is just another bag tossed on the truck as opposed to USP shipping. My first order for 1 50 pound bag of calcium chloride and 1 50 pound bag of magnesium chloride was like $35 total for both including tax. But that has since increased to about $45-50 or so.
A 50 pound bag will last literally decades on my 55g. So I give this stuff away at local frag swaps.
I am also experimenting with mixing the magnesium part with the calcium part. Seems to be working but haven't done that very long at this time anyway.
One of the real shocks with this method was the huge amount of magnesium required to do the initial adjustment. After years of running my 55g was down to 800ppm magnesium. Raising that to 1300ppm required 2-3 pounds of epsom salts. After the ninitial dose much smaller amounts are required to maintain that level. The initial calcium/alk adjustments are much smaller. I was a little nervious pouring pounds of epsom salts in the tank, but everything did just fine with no ill effects notices to either fish or corals.
my .02
