BudXsanswered grow question 5 years ago Ya dude, dont grow without it if you are recirculating. Actually, you should really be draining to waste on your coco.
If you are running a res that empties in 2-3 days, you dont need it, but you do need aeration and at least room temps or less.
For NorCal, who is a great scholar and ambitious answerer (first time grower, and amazing results so far) coco can generally be reused as a medium with a good washing
Cheers