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Neptune Systems Flow Monitoring Kit (FMK)


Item #: NS17295

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Kit Includes
  • FMM (Fluid Monitoring Module)
    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.
  • 1" Flow Sensor (FS-100)
    This flow sensor connects to the FMM, monitors the flow of water through the device, and then reports it back to your Apex via the FMM. This sensor is most often used to measure the flow in the main return line of a standard-sized aquarium. The FS-100 will work with flow rates from 150-1500 gph.
  • Two 1/2" Flow Sensors (FS-50)
    This flow sensor connects to the FMM, monitors the flow of water through the device, and then reports it back to your Apex via the FMM. Two of these are included in the FMK. These sensors are perfect for attaching to devices such as media reactors, biopellet reactors, etc. The FS-50 will work with flow rates from 30-250 gph.
  • Two 1" Unions
    To connect your FS-100 Flow sensor, Neptune Systems has included in the FMK, two 1" BSPT -> 1" Slip PVC Unions.
  • Two 1/2" Adapters
    To connect your two FS-50 Flow sensors, Neptune Systems has included in the FMK, two 1/2" BSPT -> 1/2" Slip PVC Adapters.
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 are very handy applications for the FMM. Place a flow sensor on a device like a carbon/gfo reactor and it serves many purposes. First off, you will know if your pump is not on or is faulty. 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 use either a turbine or paddle-wheel mechanism (depending on the model) to measure the flow.

With the FMK – Fluid Monitoring Kit you get one 1" Flow Sensor and unions as well as two 1/2" Flow Sensors with adapter fittings.

The FMK comes with three flow sensors but the FMM Module has a total of four ports. This means you have one port free to use for another purpose. Buy an additional flow sensor (sold separately, available also in 2" and 1/4" sizes), optical sensor or leak detection sensor and add even more functionality!

The FMM has another trick up it’s sleeve. In addition to the four sensor ports, the FMM also has a 1Link DC24 accessory port and a power supply input. This can be used to add another controllable outlet to your Apex set up. So, for instance, if you do want to set up your own ATO and attach Neptune Systsms` available PMUP or Solenoid Valve, you can do so. Simply add Neptune Systsms` 36W 24V DC power supply and the PUMP or Solenoid Valve (sold separately).

Manufacturer information

Neptune Systems Aquarium Supplies
Neptune Systems is one of the world’s leading manufacturers of aquarium controllers. The company was founded in 1995 for the purpose of developing affordable water quality monitoring and control instrumentation. Their engineering team has extensive expertise in computer hardware and software system design as well as a background in water quality analysis. Neptune Systems uses these finely-honed engineering skills to develop innovative monitoring and control solutions for use in reef and fresh water aquariums, aquaculture tanks, hydroponics systems and general laboratory use. Neptune Systems is best known for their AquaController line. The company is known for their innovation and customer centricity.

4 Stars


Reviewed on
April 24, 2020

Yes, I would recommend this.

Flow Rate

Pros: EAsily keep track of reactors and if they are getting clogged. Can dial in uv to what my needs are at the time (Pest control of Algae Control). and I know what my turnover rate is for the main tank. Perfect! Also maintenance to the unites are easy with the unions.

Cons: Have not found one yet.

Exactly what I needed for monitor the flow rates to reactors and UV unit. I did pick up one more 1" flow unit to add to this. With the manifold that i made i can control the amount of water going through the UV. and the two reactors I have runnin. All on one return pump. I after taking that flow away from the main pump I still get a reading of what is going into tank. This is great for dialing in exact amounts of water . Its a great system!

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Reviewed on
November 15, 2019

No, I would not recommend this.


Pros: None

Cons: Dose not work read the forum everyone having problem

This FMM flow is by far the worst apex Product i have purchased DO YOUR SELF A FAVOR STAY COMPLETELY AWAY FRONT THIS PRODUCT/..
Note : This is NOT Marine depot fault in anyway

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Reviewed on
March 14, 2019

Yes, I would recommend this.


Pros: Helps keep track of flow on pump for maintenance or to know pump is dying

Cons: It’s a pain to fit into a established PVC system. If you can put together in new tank build

I had a UV and thought I was getting enough flow but I was wrong this producer help me make adjustments to my UV

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Reviewed on
September 20, 2017

Yes, I would recommend this.

Real Nice Piece of Equipment

Pros: Able to see your tank flow no more off the cluff stuff.

Cons: Learning curve but so is marriage

Took a little time but once adjusted and working, the ability to monitor flow can be a valuable source of information. This company is quality all the way. Save you big bucks dollars and take the dive.

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