JUST ABOUT TO POT UP INTO A COUPLE OF ONE POT SYSTEMS WHERE THE FLOATT KEEPS THE WATER AT A CERTAIN LEVEL IN THE TRAY.MY QUESTION IS,HOW DEEP SHOULD I MAKE MY DRAINAGE UNDER MY GROWING MEDIUN,I PLAN TO USE CLAY PEBBLES AND I WASNT SURE IF THE BOTTOM OF MY BIOBIZZ MEDIUM SHOULD BE TOUCHING, I E IN DIRECT CONTACT WITH THE WATER OR WILL THE MEDIUM DRAW THE WATER UP THROUGH THE PEBBLES ITSELF,IT MAY SOUND A DAFT QUESTION BUT MY WATER IS OXYGEN FED SO IT DOSENT GO STAGNANT,I JUST NEED TO KNOW IF THE MEDIUM IS OK,WHEN STOOD IN/NEAR OR GOD KNOWS WHERE,HELP