Abstract: A fluid level controller which replaces fluid lost from a container thus maintaining the fluid level in the container. It is comprised of the following major pieces: an airtight reservoir (10) with cap (14), fill stem (12), feed lube (16), and tube attachment fittings (18a and 18b); several lengths of fluid conduit, (22a,b) and a u-bend (26) which form a siphon such that one end reaches into the bottom of reservoir (10) and the other reaches into the container below the desired fluid level; a length of conduit, (22c) which forms an air return line allowing air into reservoir (10); a stand (8) atop which sits the reservoir; a tubing clip (24); and a shut-off valve (20). The u-bend (26) allows the controller to preserve the initial prime of the system so that it only needs to be primed once. The shut-off valve (20) allows easy refilling of the controller once the fluid reservoir empties. These two features make the controller extremely easy to use.