Another suggestion is your local pool supply store...their liquid pool chlorine in gallon jugs is usually about double or more the “chlorine” strength than household bleach...would mix/dilute down much longer per gallon.
Yes. The pool shock stuff is sodium hypochlorite. I’m suspicious of it though. I suspect it has other stuff in it. You can buy calcium hypochlorite 99% pure on Amazon — at least you could three weeks ago. Still available today, maybe.
From Amazon:
Calcium Hypochlorite”Ca(OCl)2” Minimum 99% Pure! 70% Chlorine. 1 Pound Bottle
4.8 out of 5 stars 10
$14.75
FREE Shipping
But only 1 in stock today. There were a bunch in stock three weeks ago.
Anyone who buys it should download and print instructions for using it. It’s very strong and very reactive with water and other stuff.