I transfered my 75 gallon to a 240 gallon about 7 weeks ago. I transferred all of the sand from the 75 (about 100 lbs or so) and rinsed of about 150 lbs. of sand that I picked up from Prof. Mixed it all together in the 240, transfered all the rock, water, fish/corals. Did water tests everyday for two weeks. No probs at all here. The only thing I did ( to make me feel somewhat safe) make sure was to not do a water change for about 5 weeks to build up for this large water top off. You should be o.k. , gl