The FMM (Fluid Monitoring Module) is a multi-purpose module that, with the help of various accessories, enables your Apex to do: Flow Monitoring - with the various flow monitoring sensors you can monitor the flow inside the pipes of your return pump, reactor, RODI feed, and much more Leak Detection - plug in up to four leak detection probes and know you have a problem before it becomes a REAL problem Water Level Detection - attach one to four optical water level sensors and you can detect the rising or falling water levels in such applications as: water level in your sump, a full skimmate waste container, or many other possibilities Power 24VDC accessories - like PMUP and solenoid valves Future sensors - The FMM was designed such that it will be able to morph into other roles as possibilities open up from Neptune or third parties Works with ALL APEX models The FMM has another trick up it’s sleeve. In addition to the four sensor ports, the FMM also has a DC24 accessory port and a power supply input. This adds another controllable outlet to your Apex set up. So, for instance, if you do want to make your own ATO and attach our available PMUP or Solenoid Valve, you can do so. Simply add our 36W 24V DC power supply (available separately). The FMM has four ports where you can plug in various sensors and accessories (all sold separately). The best part is that they do not need to all be of the same type. This means if you want to have a flow sensor in ports 1 and 2 and then a leak detection probe in ports 3 and 4 – NO PROBLEM! Want a flow sensor for your return pump, an optical sensor for emergency sump level detection, and two leak detection probes, NO PROBLEM! Just plug them in and the FMM will automatically sense which type of sensor you have in each port.