Utah Sand

Bacteria eat the waste or pollution of Nitrogen compounds(Ammonia, Nitrite, Nitrate).
The population of Bacteria in our tanks gradually increases to meet the level of pollution being produced by the animals we introduce. In the past all that hobbyists knew to do was wait it out. They watched the Nitrogen Cycle.
That's now old school.
The need to wait 6-8 weeks for bacteria to grow before we can have a reef aquarium can be completely avoided by following the procedure outlined in the Reefkeeping Tips thread linked below in my signature line.

Tip: Algae is a powerful water cleaner that works immediately.