I’ve been struggling with clarifying my beer lately and came across some interesting info on using Whirlfloc. According to this thread, Whirlfloc wasn’t really intended to be used in homebrewing. But the manufacturer suggested when using Whirlfloc, add it to the last 5 minutes of the boil. Also, if you’re doing 5 gallon batches, 1/2 tablet is all you need.