I have a tube like that too and my ham likes it being buried. If she's in a Zoozone she can't push any of the bedding out of the cage so I'd be tempted to get as much in there as you can, she obviously likes pushing it around
Cc used to bury everything in her cage too, I just put her bowl up on a platform so she couldn't bury that and let her do what she liked with the rest of it!