Join Date: Oct 2008
Location: Redwood Coast, Nor*Cal
properly setup an overflow system is still a fine way to go for a planted tank. If you aren't injecting CO2 then there's no reason to worry about losing what you aren't putting in since the water will equalize with ambient CO2 levels and that's plenty for your plants to grow.
Since you have the sump and tank setup for an overflow, why not just use it? If you're injecting CO2 you'll want to move the pipe/tube which feeds the sump such that it empties below the operating waterline of the sump to minimize excessive splashing which will drive off your CO2. If you have a Wet/Dry sump things get more complicated and you'd be better off building or having someone build you a baffle style sump. There are a couple of ways you can also minimize your water disturbance with your overflows themselves, though that is dependent upon how they're setup.