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Pax Bellum ARID N24 Macroalgae Reactor - For Tanks 120-250 Gallons


Starting at $73/mo with . Prequalify now

Item #: 6U1424

Shipped by Pax Bellum LLC in 3-5 business days

This ingenious device utilizes macroalgae (specifically Chaetomorpha) to function as a nutrient export mechanism. The unique design of the ARID incorporates a coaxial LED light array housed in a tube to maximize light penetration and efficiency. Vapor heat pipe technology keeps the LEDs running cool for maximum light emission and lifespan while keeping the heat out of your aquarium. The LEDs were selected to supply intense PAR (photosynthetic active radiation) for rapid macroalgae growth. Maximum nutrient uptake is ensured by pushing system water evenly through the macroalgae mass.

Eliminate the clutter around your aquarium the ARID can function as a stand alone filtration system. Designed to replace GFO (granulated ferric oxide), nitrate reactors, bio-pellet reactors, carbon dosing and even protein "skimmers" (foam fractionators). The ARID can perform functions the previously mentioned equipment can`t. Functions such as, increasing and stabilizing Ph from day to night, lowering dissolved CO2 concentrations, keeping dissolved oxygen even from day to night, and increasing dissolved oxygen to levels higher than can be attained with skimmers alone, all standard benefits of running the ARID system.

Small but mighty… The N-series (aka Nano series), N18 and N24 with its acrylic construction, are marketed for the aquarist that collects and displays their kit just as passionately as they collect and display the organisms residing within the main display. The aquarist can easily remove the light cover to reveal the inner workings of the opaque acrylic chamber and inspect the growth of the macro-algae inside. Highly polished acrylic edges are found throughout the N-series. The N24 has additional chamfered edges on the lid, flange, and base. The profile of the N24 mirrors that of the C-series while the N18 striving for the smallest envelope forgoes the recognizable ARID gear shaped profile for a more simple and compact form.

The largest of the N-series, the N24 is a fully featured ARID reactor capable of handling 120-250 US gallon (450-950 liters) reef systems. The N24 ships with 250ml of 5% w/v Nitrate+Molybdenum solution and 60ml of Iron+Manganese solution. The inlet port is a reinforced ½"FNPT port in a vertical orientation integral to the base. The outlet is a ½"FNPT threaded street elbow threaded into the lid. This elbow can be removed if the outlet needs to be vertical. The unit comes with ½" barb x ½"MNPT fittings for easy plumbing using flexible vinyl tubing. The N24 now come with quick disconnects and magnetically fastened light blocking chamber cover.

Overall height of the N24 reactor is 22- 5/8", the footprint is 9-1/2" x 8-1/4". The lid, flange and base are 3/8" thick cast acrylic beautifully solvent bonded to a ¼" walled 5" diameter 18" tall clear cast acrylic chamber. Put on your sunglasses because the LED power consumption is a scant 20 watts of blinding PAR.

Have a calcium reactor? Both the N18 and N24 can accept the same optional calcium injection assembly. This plumbing kit threads directly into the water inlet on the base of the N24 and placed inline with the supply tubing on the N18. The assembly and can be installed or removed at any time by the aquarist. This add-on kit functions by creating a high pressure ¼" push-fitting port and low pressure ¼" push-fitting port by separating the two ports by a user preset valve. The valve is a union that accepts restriction discs with different port sizes to create the desired back pressure to send water to a calcium reactor. The effluent coming from the calcium reactor passes through the check valve and drip counter included in the kit, then enters the ¼" push fitting port on the low pressure side of the calcium injection assembly. This is the port below the union containing the restriction disc. There the calcium reactor effluent mixes with the bulk of the water entering the ARID, and makes contact with the macro-algae where it is stripped of excess CO2 and phosphate before entering the reef system.

Do not use in conjunction with; carbon dosing, nitrate reactors, bio-pellet reactors, GFO (granulated ferric oxide)

Pax Bellum solutions should be used to run the ARID system successfully.

Recommended Dosage

Nitrate & Molybdenum
1ml raises 100L 0.5ppm
Does as needed to maintain NO3:PO4 ratio of approx. 100:1

Iron & Manganese
1 drop per 25 gallons daily.


  • System Size: 120-250 gallons aquariums
  • Body Material: Acrylic
  • Total Height: 23"
  • Recommended Flow Rate: 180-250 gallons per hour
  • Recommended Pump: MJ1200 Pump or equivalent
  • Total Footprint: 9.5" x 8.25"
  • Hose Inlet/Outlet: ½" FNPT hose (hose and pump not included)
  • LED Power Consumption: Standard 110v / 20 Watts
    • The supplied power supply can handle 220v input power with the use of a simple adapter cord to connect to the wall socket—mainly for European use

Optional Accessories & Replacement Parts

Manufacturer information

Pax Bellum LLC was founded in 2007 as a research and development company with a focus on saltwater life support systems. From its inception, the company explored a variety of ways to achieve maximum results balancing water chemistry within closed system hobby aquariums using algae. The ARID system and the technology behind it took 13+ years to develop and refine into the recognizable product it is today. Prototypes for the ARID were trialed extensively on multiple reef systems operated by well-respected and well-known professional aquarists. The first ARID units available for public consumption debuted at MACNA 2017 in New Orleans, Louisiana, and have been popular ever since. All Pax Bellum products are made in Vermont, USA.

4 Stars


Reviewed on
February 02, 2021

Yes, I would recommend this.

Very satisfied

Pros: Compact, great quality

Cons: None

This has been a great product. No leaks. Algae grows just as advertised. I get my water tested (ICP) once a month and nitrates /phosphates are where they should be.

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Reviewed on
November 09, 2020

No, I would not recommend this.

Product doesn't work as advertised

Pros: none

Cons: Too expensive and doesn't work

Do not buy this product. i added to my tank when my nitrate level was under 10, now it's well over 50 and I'm losing corals everyday!!!

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Reviewed on
October 19, 2020

No, I would not recommend this.

Not satisified

Pros: none

Cons: Not working in my tank

I've had the Pax Bellum N24 for over 45 days running in my tank and my nitrate levels went from 5/10ppm to over 30ppm since I've added this to my tank. I am extremely disappointed with this produce. Before I was running a denitrator (Which I am considering turning back on) and my nitrates were signifcantly reduced. It ran for about a year until I made the mistake and purchased this to replace it. I definitely will not recommend this product to anyone.

Was this review helpful? 0 4


Reviewed on
April 06, 2018

Yes, I would recommend this.

It's worth buying.

It's like anything else, you get what you pay for. When it comes to plumbing, save yourself the hassle. Use 3/4 ID silicone tubing.

Was this review helpful? 0 4

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