Neptune Systems

A3 Apex Jr Aquarium Controller System

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$299.95 $299.95

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Essential Monitoring You Need Now, Expandability Later

  • Temperature, pH, Water level, & Leak Detection Monitoring
  • Instant Notifications When Something Goes Wrong
  • User-Friendly Fusion Interface
  • Two Aquabus Ports for Expansion
  • Access Your Tank From Anywhere!


Most aquarists spend more than half their day away from their aquariums, so having a system in place to notify you when something goes wrong is invaluable. The Neptune Systems Apex Jr. tracks temperature, pH, water level, and even includes a leak detector. If any of these parameters aren't quite right, you'll be notified via Neptune Systems' cloud interface, Apex Fusion. Apex can help you catch things like CO2 overdoses, heater failures, leaky canister filters, and much more before they become catastrophic problems for your tank inhabitants.


A3 Apex Jr Base Unit

The Apex Jr. Base Unit is the core of the operation. It's what connects to the Apex Fusion Cloud Interface and where all of the probes and sensors plug in as well. The base unit features a power input, two Aquabus cables for expansion, a temperature probe port, a pH probe port, and two FMM ports (for the included MOS & LD-2 Sensors)


MOS Magnetic Optical Sensor

The Magnetic Optical Sensor is specifically designed to monitor water levels. There are many ways to utilize this sensor, but one way would be to place the sensor an inch or so below the water surface and if the water level falls below the sensor, you can have the Apex notify you so that you can add water or investigate a potential leak. 

This sensor can be mounted on any aquarium or reservoir that has up to 1/4" thick walls.


LD-2 Surface Leak Detection Sensor

Neptune's LD-2 is a leak detection probe perfect for inside your stand, on hard floors, near canister filters, or any other flat surface where an overflow may cause issues. If water ever touches the sensor, your Apex will instantly notify you so corrective action can be taken and disaster avoided.


Lab Grade, Double Junction Probes 

The Apex system includes high-quality probes for monitoring your tank's temperature and pH. Calibration is a quick and simple process via the Apex Fusion dashboard, which will walk you through all the steps. In addition, the double junction pH probe will allow your readings to stay more stable without the need to calibrate as frequently. 


What's Included?

A3 Apex Jr Base Unit

Power Supply

Temperature Probe

pH Probe

MOS Magnetic Optical Sensor

LD-2 Leak Detection Sensor

pH Probe Calibration Solutions (7 & 10)

Mounting Screws

Getting Started Card

More Information
UPC 653078004977
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Product Questions

Is the A3 Apex Jr Aquarium Controller System compatible with the new DOS Quiet Drive Doser?
Question by: Darrell on May 9, 2024, 5:51 PM
Answer by: Tyler Schafer (BRS Staff) on May 10, 2024, 10:04 AM
Will I need something in addition to the Apex Jr (other than the cord) to control my dimmable Aquatic Life Hybrid T5HO fixture?
Question by: Nancy MacCrae on Mar 9, 2024, 4:36 PM
The Apex Jr. unfortunately does not come with a 0-10v output built in, so you will need this module here in order to control your lights with it: https://www.bulkreefsupply.com/led-pumps-control-module-vdm-neptune-systems.html
Answer by: Laura (BRS Staff) on May 2, 2024, 5:41 PM
So if I want to use this with everything it comes with but also the core pump and Neptune ato system, what all else do I need to buy to make it all work?
Question by: Sven Pflug on Dec 24, 2023, 7:09 AM
Hey there, you would either need an EB832 or a 1link module. Thanks!
Answer by: Codey on Jan 8, 2024, 1:18 PM
Can you use a fmk kit with this?
Question by: Scen Pflug on Apr 21, 2023, 5:56 AM
Yes you can use this with the FMK.
Answer by: Tyler Schafer (BRS Staff) on Apr 21, 2023, 12:08 PM
This can be used with the FMK.
Answer by: Tyler Schafer (BRS Staff) on Apr 21, 2023, 12:13 PM
This can be used with the FMK.
Answer by: Tyler Schafer (BRS Staff) on Apr 21, 2023, 12:28 PM
Can I use an EB8 with this?
Question by: Ryan on Oct 17, 2022, 8:58 PM
Yep! You can add an EB823 to the JR,
Answer by: William Reed (BRS Staff) on Nov 2, 2022, 10:37 AM
Does APEX Jr work with DOS system, or does that require another piece of hardware?
Question by: Tony O on Oct 5, 2022, 4:53 PM
yes, the DOS will connect to one of the two aquabus ports on the A3 APEX Jr.
Answer by: William Reed (BRS Staff) on Oct 6, 2022, 9:58 AM
Can you use the Trident with the Apex Jr?
Question by: Robert on Aug 30, 2022, 8:19 PM
Hey there,

Yes you can use the a Trident with an APEX JR. You would need a 1Link module though in order to use that and a free aquabus port on your APEX JR. You could then run the 1link cable from the Trident to the 1link module. Or alternatively you would need a free aquabus port on your APEX JR and run an aquabus cable to the Trident and then pick up the 36W 24v DC power supply to power the Trident. Thanks!
Answer by: Codey on Sep 2, 2022, 11:12 AM
Exactly what *can’t* you expand to with the Jr.? Can you, eventually, expand it to have all the capabilities of the standard Apex, or are there certain limitations you’re locked into and functions/expansions/sensors/etc. you can’t ever upgrade to with this unit?
Question by: Eli on Aug 13, 2022, 5:35 PM
Thanks for the question! The A3 Apex Jr can expand to all the modules the A3 Apex/Apex Pro can use, the only sacrifice is that you won't get the same capability out of the box and be limited to a wifi only internet connection with no option for an ethernet connection. You'll save some money by getting the regular A3 Apex, but the Apex Jr will get you started if you want just monitoring for now then control later. Let us know if we can help with anything else!
Answer by: Kyle Thomas (BRS Staff) on Aug 17, 2022, 11:21 AM
I have never used an apex before so i wanted to to know if i get the jr will it also measure salinity
Question by: Rajesh on Aug 12, 2022, 3:59 PM
Thanks for the question! The Apex Jr will not be able to measure salinity out of the box. You'll be able to do so with the additon of the PM2 Salinity Module and salinity probe purchased separately. The A3 Apex Pro will have the port for the salinity port built in, but probe would be a separate purchase. Please let us know if we can help with anything else!
Answer by: Kyle Thomas (BRS Staff) on Aug 17, 2022, 9:20 AM