I've been growing hydro and decided to give soil try. I bought some 420 growing pots(plants feed from bottom) They call for a 70% to 80% porosity. I can't buy promix or Fox Farms. All I have here is Lowe"s and they don't handle any of those type soils. Hell I can't even buy perlite without the Miracle Grow fertilize added. I do order perlite off Amazon though. So how can I mix me a batch up? I don't need any nutritional value, because I'm mixing my on nutes. Thanks