Anyone Experienced With DWC??

Just recently aquired a Bucketer DWC system, from stealth hydroponics. It is a 5 gallon bucket & i am wondering how full to fill it with water. are the hydroton cubes supposto be completely submerged in water? how full should the water be i ave been having much trouble finding answer online.

inch below the hydroton - roots should grow around the pellets and then into the water. there should be sufficient movement of the water from the airstone to break the surface