see my pic u get the idea one....
u should not see water level in the transparent chamber....only foam
and it will take time for it to settle and build the foam to go all the way up..dun keep adjusting it...as long as the water level is at the blue line or red line..foam will build up....
if it doesnt after some time....then it means your pump is not strong enough..u need a pump that can simulate about 3000litres/hr at 6ft height....
u read the pump graph...at 6ft height, the pump must still be able to pump 3000litres/hr out...as the injector provides the resistance similar to the 6ft height loss