I use a 120g tank as the fuge for my 150DT - it has ~ 6" sugar fine sand, about #60 - #80of LR/LRR, and cheato. Prior to putting the fuge online, my nitrates were pretty much impossible to test because they were so high (DT is home to a 4' Undulated Moray - a VERY messy eater) Now that the fuge has been up for ~ 1 year, the opposite has happened - even after 6 weeks without a water change, my nitrates remain virtually undetectable.