When you first put in sand or Eco like strates, at first they are basically the same as far as nutrients. Eco does add some enzymes for future absorbtion. But, as time goes by and you are dosing ferts in the water, the fish are laying down wastes, and even root tabs are used, all that gets held by the porous micro structures and absorbtion features of the man processed particles in ECO. Sand particles can absorb some too but only about 10% as efficiently. In a low tech tank it can get you by ok. But as months and even years go by, the Eco will out perform the sand as it holds and processes much more nutrients. The lighter, looser packing of the man made strates let migration of gasses and elements pass through better allowing the necessary biology of nutrient reduction and oxidation to occur. Neither sand nor the Eco like strates would ever wear out. So yes you are right that sand will work but strates like Eco are NOT a waste of money. Hope this helps. OS.