I just put this stuff in my tank 4 days ago. I know some have said to rinse it but I only had a few fish in my 55. I just pulled everything out. Drained half the water, removed all the rock gravel and poured it in. Once I had enough in I got it sloped from about 4.5" in the rear to about 2 inches in the front.
The water was so cloudy at 1st that you couldnt see the scooper in the tank. After about 30 minutes it was only about half as bad. By the next morning, it was crystal clear. Honestly I dont think the aquarium has ever been this clear. Im only using a Rena XP3 in my 55.