I belong to the KISS camp with mechanical float valve ('Wait' brand furnace humidifier valve). No electricals to worry about other than a small air pump on a timer. Gravity feed not feasible at this time since I'm running sumpless and the glass wine carboy (approx 7 gal capacity) is sitting beside the tank. Too bulky to try and raise that up. Next build will be basement sump, so it will definitely be gravity feed. Currently I pressurize the carboy using a small Stellar W60 air pump on a timer. Runs for one minute intervals throughout the day and night (about every two hours). Ok, pictures requested so here they are. Float valve and carboy. I'm sure everyone knows what an air pump looks like. There's one long and one short rigid air tube inserted through the rubber stopper on the carboy. Flex air tubes attached to rigids for air supply and water transport. Short tube comes from air pump, long tube transports the water under pressure to the mechanical float valve in the display. I fashioned the bracket for the float valve out of scrap acrylic and use nylon screws to clamp the assembly to the tank.
