Mon-Thurs 7am-5pm PST
Fri 7am-4pm PST

Questions about products, orders, shipping?
Contact us by call or email

Neptune ATK V2 Auto Top Off Kit


Item #: NS7297

Ships Free!

In Stock

What`s new with for ATK Version 2:

  • It comes with the all new PMUP v2 with improved longevity and reliability
  • Improved optical sensors

Safety Made Simple

The ATK (Automatic Top-off Kit) is a simple, standalone, and complete solution for replacing water lost to evaporation - NO APEX NECESSARY.

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.

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

PMUP Version 2

The PMUP is a multi-purpose pump that can be used for many different tasks on your aquarium.  Same great quality as the previous PMUP, but is now features an auto shut-off if the wells run dry, an over-temperature protection, new removable protective screen it stand upright on, and is easier to clean/maintain than before.

FMM -Fluid Monitoring Module

This module monitors all the sensors, tells the pump to turn on or off, and sounds an alarm when something is wrong.  It can also connect to any Apex with its AquaBus port.

Improved Optical Water Sensors

Built to provide greater longevity and reliability in a harsh marine environment.

Three Levels of Safety Prevent Overuns

  • Backup Optical Sensor: Should the main water level sensor fail, this second optical sensor is the backup. If water continues past the primary sensor, and then covers this one, the pump will be shut off and an alarm will sound.
  • IQ-Fill – Water run-time intelligence: If both the primary water sensor AND the backup optical sensor fail, the algorithm used in the ATK will not add more than double the learned water amount. It will shut itself off and sound an alarm.
  • Physical float valve – the final backstop: If for some reason all the electronic fail-safes do not work, and water is continuing to be sent to the aquarium, the mechanical float valve is the safety device that will stop the water and prevent death to your aquarium and water on your floor.


  • Plug and play ready. No mounts to assemble. No bare wires to attach.
  • 3 Levels of Safety Protection!
  • Two optical water-level sensors (one for water level and one for emergency back up)
  • IQ-Fill water run-time intelligence – learns how much water you use at each top-off
  • Mechanical float valve prevents water overrun if electronics should ever fail
  • Does NOT rely on ANY fault-prone mechanical float switches, temperature sensors, or capacitive sensors!
  • Works Standalone (NO APEX NECESSARY!)
  • Advanced features are unlocked when connected to an Apex (i.e. remote failure notification via text, email, or iOS alert)
  • Includes PMUP v2, a powerful 24VDC pump that can push water vertically up to 14`
  • Audible failure alarm
  • Additional features with optional accessories

Whats in the Box?

  • FMM – Fluid Monitoring Module (runs standalone)
  • Pre-assembled water level mechanism with:
    • Magnetic acrylic mount (works up to 1/4" glass/acrylic)
    • Two (2) optical water level sensors
    • Float valve
    • 90 degree tubing fitting
  • PMUP v2 ATO Pump
  • 24V 36W power supply
  • 4m of orange RO tubing
  • 3/8" -> 1/4" push-fit adapter fitting
  • 1/4" -> 1/4" push-fit siphon break
  • Set-screw for non-float-valve applications

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
March 25, 2021

Yes, I would recommend this.

Best ATO on the market

Pros: It’s Plug and Play as far as Hardware goes.

Cons: I wish they had designed a smaller float.

If you are a Neptune Systems User, this is a must have Item.
Very simple to install and it actually fits in the back off my IM
20 gallon Fusion, because I am running a sump less reef tank. I think it’s moderately priced as well. It can be used with
Of whiteout float ball.

Was this review helpful? 0 0


Reviewed on
November 21, 2020

Yes, I would recommend this.


Pros: Super quiet super sweet appearance

Cons: Price point could be a little better

This is the best ato I have ever used. I have had a few in the past and this thing works way more efficiently than I ever thought. You never hear it and the best part is that it can be connected to an apex so if you plan on eventually getting it you might as well get this one and expand from there. Again this thing is awesome

Was this review helpful? 0 0


Reviewed on
September 10, 2020

No, I would not recommend this.

Poor quality sensors

Pros: Integrates with Fusion

Cons: Sensors go bad

I'm on my third sensor replacement. I have used other products that seem to use the same or similar sensor and never had one go bad.

Was this review helpful? 3 0


Reviewed on
July 15, 2020

Yes, I would recommend this.

Great if setup properly

Pros: Very consistent and remote monitoring

Cons: pricey

The setup was a bit difficult, primarily because I'm new to the apex. Once I figured out how to set it up in the software and drilled the anti-siphon hole larger it works flawlessly. I am able to maintain my salinity perfectly at 1.025 in a 16 gallon nano, which is much better that any ATO I have used in the past. I did remove the float from the ATK as it wouldn't fit properly in my sump. My salinity fluctuates between 33.2-33.6 PPT throughout the day, a deviation so small that a standard refractometer couldn't detect it.

The remote monitoring with the APEX is awesome as well, it displays the salinity as well as if the upper and lower photcells are underwater.

Was this review helpful? 2 0


Reviewed on
July 04, 2020

Yes, I would recommend this.

Great product

Very quick and easy to install

Was this review helpful? 0 0


Reviewed on
July 03, 2020

Yes, I would recommend this.

Great top off solution

Pros: Ease of use and setup, Reliability, and connectivity.

Cons: None

I love that you get everything in one box to do top off in your tank. Easy to set up and a lot of redundancy to protect from a water over fill situation. It can be used stand alone of connected to your Neptune controller. I love the magnetic bracket that holds all of the sensors and manual float valve.I have seen a few people say the pump is noisy, but it really isn't that bad especially since it only runs occasionaly.

Was this review helpful? 0 0


Reviewed on
April 19, 2020

Yes, I would recommend this.

Excellent Product

Pros: Ease of installation

Cons: None found

I received ATK quickly and installation on my sump was a breeze. Set up instructions were clear and easy to follow. After two months ATK functions exactly as advertised

Was this review helpful? 0 0


Reviewed on
February 12, 2020

Yes, I would recommend this.

Great product!

Pros: Reliable, seedless integration with Apex controllers

Cons: Pump noise

The Apex ATK is a great product. Pump is a bit noisy but aside from that well worth the investment and makes maintaining my nano reefs water topping off a breeze. Integrates seamlessly with the Apex EL or the Apex Jr when the proper add on modules are used. Would highly recommend to those that use any of the Apex controllers.

Was this review helpful? 2 0


Reviewed on
January 26, 2020

No, I would not recommend this.

Never worked correctly

Cons: Came broken out of the box

Never worked. I threw it in the trash. Warranty?😂😂
Very bad unit

Was this review helpful? 0 0


Reviewed on
October 21, 2019

No, I would not recommend this.

Piece of crap

Cons: Very defective

Do not buy this. You would be better off lighting 2 $100 bills on fire. This literally came with all 3 components not functioning out of the box brand new. I wasted countless hours on this. I kept thinking it can’t possibly be all defective. After about a month ( I had to send each piece back one at a time so they could verify it was broken, took about a week each time). The word warranty is a sick joke. You must email and schedule a time to speak with someone during very limited hours. My schedule doesn’t work that way. Do yourself a favor and buy a tunze. I absolutely regret buying this turd and would never buy another Neptune system ever again. To be fair my dos pumps work great and the rest of my Neptune system functions correctly, but the support from them absolutely sucks! It simply doesn’t take into account that you have a reef tank with thousands of dollars worth of occupants that just don’t have weeks to wait because Neptune sells defective items.

Was this review helpful? 0 0

We use cookies to provide a personalized site experience. By continuing to use & browse this site, you agree to our Privacy Policy.