I used Natures Ocean brand Bio-active live agronite sand in my tank.It replaced my nasty crushed coral substrate with out a cycle.I removed all the CC and put in 40lbs of sand in a day.The only problem was the cloudy water caused by removing the CC.But that cleared in a day.Since then I have added an additional 60lbs of the same sand putting the total at 100lbs.I love this stuff,and highly reccomend it.