Hi Jenksie,
I used the bucket method to clean my playsand. Put sand in bucket, add water, swirl hand around in sand to stir it up, pour water out. Repeat until water runoff is clear.
You may find that even after rinsing the sand thorougly there will be a little bit of cloudiness in the water for a couple of days. To prevent this, after putting the sand in the tank, place a plate on top of the sand and direct the pouring water onto the plate rather than the sand.
The good news is you only need to lightly cover the tank base with sand.
Most of my tanks have a centimeter depth at most. If more than an inch of sand base depth is in the tank, you run the risk of gas pockets developing under the surface.
I used the remaining sand to fill in some cracks in the garden path