Silicia sand is inert. It is harmless. If you use only sand for substrate you have to use ferts. Many use root tabs.
I had it in a 10 gallon tank over dirt, El Natural style. Since we had a water shortage at time I set it up, I just rinsed the sand 1x. It took a few weeks for the cloud to go away. It got ugly after 3 months. It was impossible to get the mulm off. Recently put it in a 29 gallon tank with the sand in the front with no plants in it. Didn't rinse it. Just added nutrafin clear. It didn't get very cloudy and cleared up in a few weeks.
Hoppy is using it over a RUGF in his tank:
http://www.plantedtank.net/forums/diy/78505-rfug-blast-past-diy.html
I had it in a 10 gallon tank over dirt, El Natural style. Since we had a water shortage at time I set it up, I just rinsed the sand 1x. It took a few weeks for the cloud to go away. It got ugly after 3 months. It was impossible to get the mulm off. Recently put it in a 29 gallon tank with the sand in the front with no plants in it. Didn't rinse it. Just added nutrafin clear. It didn't get very cloudy and cleared up in a few weeks.
Hoppy is using it over a RUGF in his tank:
http://www.plantedtank.net/forums/diy/78505-rfug-blast-past-diy.html