If it's a constant drip or a various type hydro system then it's fine...alot of people use various things to suspend the plants roots in...heck you can use marbles or lego's if you want...does'nt really matter much as long as they stay moist and have balanced nutrients and the roots have ample space to grow. In a pot though growing like "soil" I would say definitely add more to the mix like coconut fiber and/or spaghnum peat moss otherwise you will surely have some imbalances and it could dry out too much and stunt or kill the plants plus it does'nt offer much support to roots as it's extremely lightweight and overly porous. Best bet is to use a high quality potting soil for your "pot"