Neptune Systems Apex Flow Sensor - 1/4″ with push-fit connectors (FS-25)Neptune Systems Apex Flow Sensor 1 4 with push fit connectors (FS 25) Usually used with aquarium accessories like RODI inputs, calcium reactor feed lines etc., this flow sensor can be placed in line with the flow on 1 4 tubing, connected to the FMM, and communicate to your Apex the flow rate of water through that pipe. The flow sensor itself uses push fit connectors to make connecting to your system as simple as possible. The FS 25 will work with flow