I've had great results with rinsing it and using a piece of plastic to cover it completely as I fill the tank. Maybe you got an off bag?
More details ~ I put about a large coffee can's worth in a bucket and run water in it as I stir it with both hands, letting the water overflow the top of the bucket and pouring all the water out and refilling a few times. This shouldn't take more than five minutes. It never will run completely clear, but the water will change from being almost coffee-dark at first to being more like weakish tea. Drain and dump in the tank. I used three or four coffee cans' worth for a ten gallon tank about 3" deep.
Next, I took a hint from Jen ~ I laid a piece of plastic wrap across the top, all the way to the edges on all four sides. Then I filled it using my gravel vac, putting the bucket higher than the tank of course and letting it slowly siphon into the tank. I put the end of the hose in the middle of the plastic. Once full, the tank was almost totally clear! No more cloudy than a light new-tank bacterial bloom.
I did three tanks that day and the other two were a bit cloudier, I think because I reused the same piece of plastic I'd used on the other clear tank. Since it was wet, it was harder to get it to spread out flat all the way to all four edges. But they were still nothing like the tank I did a month before using a plate to fill it. THAT one took DAYS and a few clams to clear.