In the Past ive had to Clean Lots and Lots of Sand and have done so by simply mixing Fresh Water into a Half full 5 Gallon Bucket and Rinsing untill Water becomes CLEAR

VERY VERY VERY VERY VERY TIME CONSUMING but Cheaper then Buying New !

just make sure you let water settle in tank after newly washed sand has been introduced and that you SEED the tank with some Good Live Sand to Start up a Cycle