newfishies, what you will end up with is the sand on the bottom and the flourite on top. All of the fine grained sand will start to settle in and the larger flourite will come to the top. It may take a while but the gentle vibration will cause it. It you want to see how it works, put some larger gravel in the bottom of a bucket and then cover it good with sand. Now start tapping or shaking the bucket. It won't be long before they change places. I am already experiencing it in my 75 gallon and it has only been set up for 2 weeks. It has Eco Complete Planted on the bottom and Tahitian Moon Sand on top. I can already see the courser rock coming up.newfishies said:i also put a layer of flourite on the bottom of the tanks, as i am going to be planting them next!!