You are about to get a million answers and a few angry folks trying to prove that their way is the only way! Each method has its own pros and cons, but when it comes to sand beds there are three main methods. 1) no sand is easy to maintain and you can use lots of flow! You will need different equipment to help remove the nitrogen cycle products. 2) less than four inch sand bed or large particle sand bed is pleasant to look at and is relatively easy to maintain. It will not produce much support for the live rock and will not support much bacteria life. Will need some equipment to help remove nitrate. 3) Deep sand bed is at least 4 inches of fine sand. Takes up valuable space and many people do not like the look. If various live sand critters are introduced you will never have to worry about any of the nitrogen cycle products, including nitrate. It provides great support for live rock and requires no maintenance.