PFS is perfectly fine for aquarium usage. I use it in all of my tanks as do many other members of the forum. Be sure it rinse rinse rinse rinse rinse before putting it in the tank or it will cloud your aquarium for a while. Fill a bucket 1/3 full of sand. Put the garden hose in the bucket and let it fill. Swish the sand around with the hose to kick upall the debris/dust. Let the bucket overflow. Keep doing this until the water comes out clear.