I've used sand in small setups. What I've done is to put about 5" or so in the bottom of a 5g bucket. Then stick a hose in there on full blast and tip the bucket so the cloud drains and the granules remain. Sustain, repeat as desired until the hose only stirs up large grains which settle easily. Add to tank. Fill bucket with fresh sand, repeat. HTH.
I have had great success useing old(or new)window screens for the washing of gravel or sand. Placed a few inches off the ground(over the lawn so as not to waste the water) run the water through the sand placed in the middle of the screen. Use of a large screen helps with volume, however, supporting the screen with egg crate or a suitable porous material will help prevent ripping the screen especially if it is old.
If the sand or gravel is to fine, bucket method....just kind of tedious if your doing like 200#of sand...