you have to match the intake GPH to the export GPH a simple hose syphoning from the tank is not going to pull enough water out of the DT as the 600 PH is returning so in case, you will flood the DT and flood meaning water overflowing from your tank and vise versa....if the syphon is pulling more water then what the 600 ph is returning you will flood your fuge...the proper way to do this is to get the tank drilled and run pvc as a run off to the fuge or get a HOB overflow that is rated to intake as much water as your pump is going to export from the fuge back to the DT!