Neptune Systems

ATK V2 Auto Top Off Kit

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$239.99 $239.99

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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!

  • 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


No aquarium task is more tedious than adding freshwater to replace the water that evaporates out of our aquariums each day. Because of this, it's no surprise that an auto top off system (ATO) is usually the first piece of automation equipment purchased by new hobbyists. Having an ATO is particularly useful when you're away on vacation and don't have someone to watch over your aquarium or simply want to go a few days without having to think about your tank.

The ATK Auto Top Off Kit from Neptune Systems is simple to install, works with or without an Apex Controller, and has multiple back-up safety measures to prevent overfilling.


Three Levels of Safety

  1. Backup Optical Sensor: If the primary water level sensor fails, a backup optical sensor will stop the ATO pump and an alarm will sound.
  2. IQ-Fill (stand-alone mode only): The ATK will not add more than double the learned water amount. If the system is running for too long, it will stop the ATO pump and an alarm will sound.
  3. Physical Float Valve: In the rare event that the electronic failsafes do not work, a mechanical float valve will stop water from flowing into your aquarium.


PMUP v2 ATO Pump

The PMUP is a small utility pump that is perfect for moving water from your RODI reservoir to the aquarium or sump. This pump has a vertical design that easily drops into most water jugs or ATO reservoirs and can pump water over 14 feet vertically, allowing for efficient water delivery from remote or lower-floor reservoirs.

The bottom of the pump features a removable screen for easy access to the pump's impeller. This design keeps potential debris out of the pump while also allowing easy access for cleaning. 


Extra Value for Apex Owners

If you already have an Apex, setting up the ATK is still super-simple. Just plug in all the components, attach it to your Apex via the AquaBus cable, and run the set-up task in Apex Fusion. With the ATK connected to an Apex, you get the added benefit of having email and push notifications if something goes wrong and you can integrate the ATK into other functions.

The FMM module included with the ATK has four ports for sensors and probes. The two optical sensors included with the ATK only use port-1 and port-2, which means there are two free ports that can be used for additional accessories like leak detectors, flow sensors, and additional optical sensors.


What's Included?

FMM Fluid Monitoring Module

(2x) Optical Water Level Sensors

Float Valve

90° Tube Fitting


4 Meters Orange RO Tubing

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

1/4" Push Connect Siphon Break

Set Screw for Non-Float Valve Applications

24V 36W Power Supply

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
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Product Questions

Hi, is there an online manual somewhere with more information? I’m not sure I set mine up right. When it’s time to top off, it just beeps and flashes red.
Question by: Pam C on Mar 13, 2024, 12:24 PM
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