Look, the cloudiness in sand is caused by silt. Not the sand itself. If you wash the sand, most of the silt goes away. Now, there may be some silt left. It's easy to get rid of:
1. Put in lots of clean filter wool in the filter. Has to be brand new wool.
2. Add a few drops of "Filter Aid" (there are various brands). This clumps silt into bigger bits, and the big bits get caught in the wool.
Easy as pie, and guaranteed to work in 24 hours. Done this many, many times. Next time you clean the filter, you'll find the wool pretty messy. That's the silt! Great for your garden, by the way.
Cheers,
Neale