TOM TM1353 Aquarium Auto Fill System stand-alone, connect 3/4 bulk head. KollerCraft is highly regarded for supplying superior quality, innovative pet products and reliable service. This Auto Fill system has a unique gravity fed water replacement system. It also compensates for water evaporation, adding make-up water slowly back into the aquarium as needed. Holds up to 3.5 gallons of make-up water.