Hey mujtba, I would be willing to bet that your problem is that you did not rinse the sand properly. I bought some tropical play sand at Home Depot that was extremely powdery. I had to start out with it in a bucket and rinse it. What i did was fill the 5 gallon bucket about a third of the way with sand and rinse with water, stirring the sand as you add the water until the bucket is full. Let the mixture settle for about 20 seconds then slowly dump the water out of the bucket paying attention not to empty too much sand out with it. Most of the sand will stay at the bottom while you do this, but some will be suspended in the water along with the powder. Repeat this process until you are satisfied that you aren't going to get any more powder out then add it to your tank. Do this with you entire load of sand and your tank will clear up in a matter of days. I know this is a long, drawn out process, but with the money saved on the sand and obviously the time saved without a cloudy tank, it is well worth it. My tank no longer gets sand powder stirred up at all.
