sand, stay away from course and CC
. Why vacuum when you don't have to? Get a Clean up crew big enough to handle the job and sit back and watch the tank. Use between 1-3" and you will be fine. You should not be using a large PH
that will be blowing the sand all over the tank get one big enough to do the job and have it blowing up for surface agitation not down. Use a smaller one if needed for bottom movement.