CF systems need the set water level (by standpipe) to be lower than other style systems. Purely for the 'wicking' effect.
A water level set in the GB of a CF system will have an accelerated or more aggressive wicking action due to the constant availability of water at that height.
For example, when I switched from F&D to CF I had to cut about an inch from my standpipe because the constant inflow of water at the original standpipe height caused the water to wick so intensely that my surface media was soaked. This caused issues with root rot and fungal issues.
I had to experiment cutting the standpipe down piece by piece till I found the desired hieght. Remember that plant roots actually dive quite deep in search for nutrient so water to the surface or even a few inches below is not really required for a mature plant. Only seeds need a bit of surface 'dampness' so to speak.
I have set my standpipe so that when I break the surface of the media with my hand I find damp media, this is where I sow my seeds.... which works beautifully.
