Flourite is notoriously hard to get completely free of sediment before you put it in your tank. If you do not take the time to thoroughly rinse it, however, you will wind up with a cloudy tank that lasts and lasts. I take mine a bit at a time and place it in a bucket. I then spray the bucket with water from a hose making sure to churn the gravel a lot to release all the sediment. When the water starts to come out of the bucket pretty clear, I stop and repeat with another load of gravel.
I've never tried the "dry out" method proposed by pineapple, but if you do, I'd like to hear your experience with it.