AutoTopoff 12v ATO System w/ Pump or Solenoid Valve Basic and reliable ATO using a high quality magnetic reed float switch.  We've found float switches to be the most reliable type of ATO sensor!     Refill your aquarium directly from your RO system with the solenoid valve. The solenoid valve has 1/4" quick-connect fittings for use with 1/4" OD tubing commonly used with reverse osmosis filter systems.   Or opt for the pump version and refill your tank from a reservoir.  The pump uses 1/4" ID tubing, 60GPH with a max head of 200"  (that's over 16 feet!). The ATO turns on power when the float is low to energize the solenoid valve or pump which refills your tank.  The float switch requires 1.75" x 1" x 2.25" high for mounting.  The 1/2" bracket will fit over a tank wall up to 1/2" thick, the 1" bracket will fit over a 1" thick tank wall.  Bracket extends ~7" down into your tank. Power switching is done with a 10 amp double pole relay wired using both sets of contacts which reduces contact wear and provides you an additional switch for redundancy.   2 year warranty on the controller, 90 day warranty on the pump/solenoid valve.