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Fluid Monitoring Module (Module Only) - Neptune Systems

Neptune Systems

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Product Description


This is just the module itself without and sensors.

The FMM (Fluid Monitoring Module) is a module that connects to any Apex (Apex(2016), Apex Classic, Apex Lite, Apex Jr.) via it’s AquaBus port providing four multi-function monitoring ports that can be used for flow sensors, water-level sensors, leak detections sensors and possibly future products as well.

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.

The FMM (Fluid Monitoring Module) is a multi-purpose module that, with the help of various accessories, enables your Apex to do:

  • Flow Monitoring
  • Leak Detection
  • Water Level Detection
  • Power 24VDC accessories
  • Future sensors

Return pump
Measuring the flow of your aquarium’s main return pump is an incredibly useful piece of information. The key benefit would be to have the Apex notify you the instant the flow stops for any reason — usually the result of a failed or faulty pump. Furthermore, an indication of a reduced flow rate could be used to determine that the pump or the lines are dirty or are becoming clogged with algae, debris, animals, or the growth of organisms inside your plumbing.

Auxiliary pumps on reactors and the like
This is a very handy application for the FMM. Place a flow sensor on a device like a carbon/gfo/biopellet reactor and it serves many purposes. First off, you will know if your pump is not not flowing correctly or failed altogether. Next, you can easily fine-tune the flow into the reactor by watching the dashboard tile on your Apex. Finally, you can know when the reactor is becoming clogged with detritus or possibly channeling has occurred by an alert on your Apex or by monitoring your dashboard.

Put a flow sensor inline to your device, plug it in to the FMM, and see exactly the flow rate of the water (any aquarium fluid really) going through that sensor. The industrial-grade flow sensors work use either a turbine or paddle-wheel mechanism (depending on the model) to measure the flow.

It is important to note that the flow rate that will be reported back to you from the flow sensors will likely be far lower than you expect or what is printed on the pump label or documentation. This is due to head pressure loss from physical height differences, long runs, restrictions such as ball valves, fittings like elbows, tees, and reducers, and then finally the loc-line many use as the entry point into their tanks. As an example, a pump rated at 3200gph will likely be showing less than half that amount in nearly all applications.


The FMK comes with three flow sensors but the FMM has a total of four ports. This means you have one port free to use for another purpose. Buy additional flow sensors (available also in 2″ and 1/4″ sizes) or choose from one of the options below and add even more functionality!


There are many useful purposes for water-level sensors on an aquarium. They can help you build an auto-top-off, monitor the levels in your supplement containers, even help automate saltwater mixing containers. Traditionally float switches have been the most commonly used types of these devices, however they are prone to all kinds of failure. On the other hand, the solid-state, optically-controlled sensors used with the FMM are much more reliable and dependable.

These optical sensors work by using an LED emitter and receptor in a clear enclosure such that when it becomes wet, the light bends and no longer completes the circuit.

Easy to use
Of course you could always add water-level sensors to your Apex – but it was more complicated than most users could handle. Now, with the FMM and these optical water-level sensors, you just plug them in! No wire-stripping, no breakout box necessary!


In addition to flow monitoring and level-detection, the FMM can be used for leak detection. Simply plug in up to four of our new, super-sensitive leak detection probes and place them where you want that oh-so-important protection for your floors, and your marriage! There is one sensor for solid surfaces and another slimline version for use under carpets.


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).









Product Videos

FMK - Flow Monitoring Kit :: Know your Flow! :: An Accessory for your Apex by Neptune Systems 09:26

In this video learn all about the new FMK from Neptune Systems. The FMK includes the FMM (Fluid Monitoring Module), one 1" flow sensor, and two 1/2" flow sensors. More product info can be found at or

  • FMK - Flow Mon...
    In this video learn all about the new FMK from Neptune Systems...

Product Reviews

Write Review

  1. Almost perfect

    Posted by Unknown on Mar 26th 2017

    If you have a full apex this will be great. I have a Jr and wanted this for leak detection and to use as an ATO. Apparently there's a bug preventing the leak sensors from being seen by the apex. Apex customer service has been great and they assured me they should have a firmware fix within a week or so.

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