Hi, "can you reuses Coco?" Yes is the short answer! "How do I get rid of the old roots?" Just let it dry out (like a desert) hold on to the stem and gently shake as you pull the root ball out! Now, depending on growing style, your using biobizz soil with Canna Terra nutes, once you are at harvest 'FLUSH WELL' Harvest your plant let the Coco dry remove root all, add a "little" more Coco (you will lose some during growing/drying/reusing the Coco) RE- buffer the Coco and should be good to go, happy growing 👍