Dichlor is fine - given cold water, you'll need to pre-dissolve it, to keep it from sitting on the bottom.

The problem is the 53% . . . if it's 53% available chlorine, you're OK. If it's 53% dichlor + 47% other stuff, not so good. Some of the other stuff they blend with, is not what you want to put in your pool. If you can tell us brand and EXACT product name, we can probably find out.