First I would take the sand and rinse it very well in a bucket. Use a hose with water and keep sending the beam of water into the bottom of the bucket, pour off dirty water and repeat until sand is reasonably clean.
After that if you want to make sure you dont get any clouding in the tank you can fill a 1,5 liter soda bottle with sand and water, put this into the tank and then tip it upside down. The sand should gently pour out of the bottle with minimal disturbance. Most of the cloudy water should stay inside the bottle