I am thinking about putting new sand in my reef tank.I have had it set up for 5 years now,i used old sand from a freinds tank 5 years ago.now i am not happy with it because he used a combonation sand puca shells crushed coral.now all the crushed coral and puca shells are on top.Would i cause any problems if i took out all of the old and replaced it with new?Any suggestions



