Neptune Systems

ATK V2 Auto Top Off Kit

In stock

- +

Don't have an Apex? No Problem!

The ATK has a stand-alone mode, so no Apex Controller is required.

A Complete, Simple, & Standalone ATO!

If you want a safe ATO system, the Neptune System ATK v2 uses a mixture of optical eyes and a float valve to ensure your tanks water level stays the same while preventing overfills. With the ATK v2 you do not need an Apex Controller since it can be run 100% standalone, however with the addition of an Apex Controller additional features can be unlocked and more accessories can be added to the included FMM module. 

  • Plug & Play Operation
  • Includes Powerful 24V DC PMUP  
  • Two Optical Sensors With No Moving Parts
  • IQ-Fill Water Run-Time Intelligence
  • Mechanical Float Valve
  • Audible Alarms
  • No Apex Necessary
  • Advanced Featured Unlocked When Paired With Apex Controllers


The ATK (Automatic Top-off Kit) is a simple, standalone, and complete solution for replacing water lost to evaporation.

The new aquarium hobbyist has many challenges, but none is more annoying than the chore of adding water, every day, to make up for that lost to evaporation (a.k.a. topping off/up). This alone usually makes the automatic top-off (ATO) device the first piece of automation equipment purchased.

The ironic flip side of this decision is that a faulty ATO device is one of the leading reasons for catastrophic aquarium failure, or even worse, flooding of the house or business.

Not all ATO devices are created equal. Sadly, many ATO on the market are made with cheap components, have very little protection against these catastrophes, and are just a nightmare to assemble and install correctly.

An ATO does not have to be both a blessing and a curse!

Neptune Systems designed our ATK – Automatic Top-Off Kit to not only be super-simple to install and use, but it is unique in the market as an ATO device with three layers of redundant monitoring and water-level control. The ATK does the work for you, while at the same time protecting your tank and your home.


Safer Than You Can See

The Neptune Systems ATK v2 uses the robust Fluid Metering Module with re-designed optical sensors to monitor your water level. The dual sensor design allows for the ATK to have one main water level sensor and the other as a backup should the first ever get dirty. On top of the optical sensors, a mechanical float valve is integrated into the pre-assembled water level mechanism that will protect you against the super rare electronics failure. On-top of all that, IQ-Fill technology will learn and limit the run-time limits for your aquarium system, ensuring that if all else fails, the PMUPv2 never runs long enough to overfill your aquarium. 


Two Accessory Ports Let You Expand Your ATK

The FMM module included with the ATK has four ports for sensors and probes. The two installed optical sensors for the ATK only use port-1 and port-2. This means there are two free ports that can be used for these optional purposes.


Optical Sensors with Magnetic Mounts

Whether for your ATO reservoir, to use as a sump-high alert, or for your long term water storage such as a brute container, these optical sensors plugin into the FMM. In standalone use when used in your ATO reservoir (plugged into port-4), the FMM will stop your PMUP and sound an alarm when the sensor is above the water level. If you plug it into port-3, and mount it high in your sump, if your water level ever goes that high, an alarm will sound and your PMUP will stop operating.


Optional leak detection probes.

Insert one of our leak detection probes into port-3 on the FMM and then place it near your sump. Now, if for some reason your sump should ever overflow, your ATK will stop operating and an alarm will sound.


Flow sensors in sizes from 1/4″ to 2″ (Apex-connected mode only)

Optional sensors are available that will monitor the flow through plumbing on your aquarium. This is perfect for monitoring the health of your return pump, keeping an eye on your emergency drain, setting the levels on your various reactors and filters, or watching the flow to your RODI.



What's Included?

1x FMM Fluid Monitoring Module

2x Optical Water Level Sensors

1x Float Valve

1x 90° Tube Fitting

1x PMUPv2

1x 4 Meters Orange RO Tubing

1x 3/8" to 1/4" Push Connect Adapter Fitting

1x 1/4" Push Connect Siphon Break

1x Set Screw for Non-Float Valve Applications



More Information
UPC 653078004571
Dimensions (Pump) 4.58" H x 2.24" Diameter
Included Mounting Magnetic
Control Type WiFi / App (with optional controller), Preset Plug & Play (No Controls)
Pump Included Yes
Pump Model Neptune Systems 24V DC PMUP v2
Flow Rate 100 GPH
Tubing Length 13 Feet
Power Type DC
Power Consumption 17 watts
Power Cord Length 6 Feet
Additional Notes Can be run standalone, but additional control features and alarm types (text, email, mobile alerts) available only when paired with an Apex controller
Water Level Detection Float Valve or Switch, Optical Sensor
Alarms Audible, Visual, Mobile Alert, Email
Safety Features Overflow Timer, Run-Dry Protection, Includes Anti-Siphon Valve
Max Head Height 10 - 15 Feet
Write Your Own Review
You're reviewing:ATK V2 Auto Top Off Kit
Your Rating
Only registered users can write reviews. Please or

Product Questions

Will this work with an Apex Junior?
Question by: Kelley McIntyre on Jan 19, 2023, 5:57 AM
Hey There, thanks for the question! Yes it will
Answer by: James Johnson (BRS Staff) on Feb 9, 2023, 1:22 PM
Is this compatible with the apex el?
Question by: Mike carr on Jan 18, 2023, 4:17 PM
Hey Mike, thanks for the question! Yes it is!
Answer by: James Johnson (BRS Staff) on Feb 9, 2023, 11:20 AM
Can both magnet sides be under water? I assume so if the internal magnet can be under water and my "external" magnet looks to be protected by a similar housing.

My return pump chamber can only fit the float valve if the "external mount" is inside my skimmer chamber. If I flip the float magnet to the outer wall of my sump, the float valve hits my return pump tubing.

Question by: Bryan Trach on Jan 10, 2023, 9:07 PM
Hey there,
Thank you for reaching out to us. Yes, both magnets can be underwater.

Please let me know if you need anything further and take care!
Answer by: Matt Lucero (BRS Staff) on Jan 12, 2023, 10:46 AM
Where in the sump would you put the optical sensors?
Question by: Sven Pflug on Jan 6, 2023, 8:17 AM
Typically you'd put it in the return pump chamber as that is the chamber where the evaporation will affect the water level.
Answer by: William Reed (BRS Staff) on Jan 12, 2023, 4:04 PM
I already have the FMM Module. Can I buy everything except the FMM?
Question by: Doug on Dec 27, 2022, 9:16 PM
Unfortunately this only comes as an entire kit.
Answer by: William Reed (BRS Staff) on Dec 30, 2022, 4:22 PM
What is the max head of this pump? I’d like to set up my auto reservoir one floor below my tank.
Question by: Dan on Jun 4, 2022, 8:29 PM
Thanks for the question! While we don't have an exact number shared with us here at BRS, we do have a user that has used this to top off from the basement to their tank the floor above. Keep in mind that you will have to use an Apex in this application that way you can allow the PMUP to run for more than 5 minutes before timing out into an error condition.
Answer by: Kyle Thomas (BRS Staff) on Jun 7, 2022, 11:09 AM
Do I have to use the power adapter to the fmm module with my Existing Apex System? Or can it plug directly into the Apex head or EB832 without the power brick?
Question by: Michael Morin on Mar 23, 2022, 12:41 AM
Hey Michael, you can plug this directly into the APEX/EB832 for power. Power supply is only neccessary for stand alone application
Answer by: James Johnson (BRS Staff) on Mar 24, 2022, 3:26 PM
I already have a FMM module with two leak sensors. Can I just buy a PMUP, the float valve/mount, 2 OS-1 V2 sensors and the tubing connectors?
Question by: Dan Luongo on Jan 1, 2022, 9:04 AM
Thank you for your question. Unfortunately the ATK kit is the only way to get the mount with the sensor, float, and tubing connectors at this time.
Answer by: Rick Pucciarella (BRS Staff) on Feb 4, 2022, 12:28 PM
What are the dimensions of the portion that sits inside the tank, float arm included? I'm trying to find out if this will fit in the back of a IM 40?
Question by: Spencer on Dec 9, 2021, 2:29 PM
I do not know the exact dims but I do know that a few people here have used this in the back of the IM40 and the smaller AIO tanks.
Answer by: Tyler Schafer (BRS Staff) on Dec 17, 2021, 10:25 AM
Could a solenoid be hooked to this system instead of the pump and then be plumbed direct to ro/DI system?
Question by: Mike Herron on Dec 6, 2019, 12:12 AM
Hey there!

In theory it would work, just pair the FMM with the solenoid instead of the pump. We do not at all recommend this because you will have it hooked to a endless supply of water and if the solenoid or sensors fail that would be bad news.
Answer by: Thomas Billington on Dec 6, 2019, 11:45 AM