Good to know though they take longer than 5 minutes to dissolve.
Wow, you must have some tough Whirfloc! When I add 1/2 tab it dissolves almost instantly.
I add mine at 10 minutes and I crush it with the back of a spoon before adding it. And yes, it does fizz when you add it. I always imagine I'm making some potion and this is the ingredient that goes "poof" and makes the skull and crossbones appear above the kettle like in the Bugs Bunny cartoons.