More questions! Looking into sand as the substrate. Pool filter sand has been suggested, also washed play sand. Some of the sand and quarry companies advertise river sand. Some state that it is actual river sand. Some other stuff is crushed quartz or what just looks like unwashed play sand. Anyone used the stuff? Would be nice if there was a happy medium between the aquarium suppliers sand which is obscenely expensive for small quantities and quarry/landscape suppliers which is cheap and in bulk.