I was wondering whta the best way to go from gravel to sand in my tank was. I probably should have set it up with sand but I thought that the combination of gravel that I used would look neat. Now seeing all of these sand tanks now I really want to change. I have 2 empty small tanks that I can put my fish in temperarily and I could put 1 or 2 in my 7. Should drain the water and start over or just take out the gravel and put sand in? Also how long does it take for the sand to settle down in the tank (and not be so cloudy)?