Unless your changing your
nutrient every week or so, it does not hurt to oxegenate it. Helps in uptake and more importantly keeps nutrient from stagnating. Keeping the nutrient well oxygenated also swings the microbial equilibrium in factor of the beneficial microbes in the nutrient, as does starting with a clean system and equipment. So, start with clean system (i.e, 10% bleach clean out, rinse, fill then oxogenate nutrient.