hey guys

Im very new to hydroponics so I got a question. I set up a water culture system, the net cups have coco-tek and expandable pellets. The problem is that all the coco-tek is falling in the water until there's no more left. I think its because the airstone lets out so many bubbles it breaks the coco apart and let it fall through the cups. So should I fill the net cups with the pellets first then add the coco on top of that so the bubbles only touch the pellets instead of the coco? The reason I'm asking that is because i'm not sure if its ok to just have the pellets get wet instead of the coco. Or if i should just leave it like that and its normal for the coco to all fall in the water

thanks in advance!