Pax Bellum LLC

Pax Bellum ARID C30 Macroalgae Reactor - For Tanks 250-500 Gallons


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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.

Big and sexy… The C-series (aka Commercial series), C30 and C36 are stout reactors constructed of US made PVC that can handle the largest residential aquariums, or fit right at home behind the scenes of a public aquarium. The flanges’ bolt-hole circle features stainless steel female threaded inserts, mated to hex head button cap screws. The metal on metal thread engagement makes for the strongest possible clamping force between the lid and flange, and virtually eliminating the possibility of stripped threads. Protecting the lid from the 316L stainless hardware, nylon washers are placed below the heads of each screw and rubber tubes protect the threads from direct contact with the acrylic lid. Sealing the lid is a quad-ring for twice the sealing surface of an ordinary o-ring. The flanges and bases are solvent bonded for a clean look with monolithic strength.

The C30 and C36 models have the recognizable lid and flange profile for easy one-handed opening. Both models have ¾" FNPT stainless steel reinforced inlet ports and 3/4" threaded street elbows that thread into the lid for the outlet. Both come standard with un-valved quick disconnect fittings on the inlet and outlet threaded ¾ MPT x ¾" hose barb. All edges are chamfered and both the PVC chamber and acrylic lid come polished. The lids are engraved with the company name, model, and US Patent numbers. Clear legs and piping underneath give the reactors ground-effects lighting for an out of worldly look. Attention to detail is seen throughout the bullet proof construction of the C30 and C36.

The C30 model is for systems of 250-500 US gallons in volume (950-1900 liters). The total height is 30" with a footprint of 11-1/2"x 10". The chamber is 6" in diameter and 24" tall. LED power consumption is 28 watts. This model includes starter supplements; 500ml of Nitrate+Molybdenum and 125ml of Iron+Manganese.

Have a calcium reactor? Both the C30 and C36 can accept the same optional calcium injection assembly. This plumbing kit threads directly into the water inlet on the base of the ARID 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 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 supplements 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: 250-500 gallon aquariums
  • Body Material: PVC
  • Total Height: 30"
  • Recommended Flow Rate: 300-500 gallons per hour
  • Recommended Pump: Mag Drive 7, Pan World 40PX, or equivalent
  • Total Footprint: 13" x 12"
  • Hose Inlet/Outlet: ¾" FNPT hose (hose and pump not included)
  • LED Power Consumption: Standard 110v / 42 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

Connect to a Calcium Reactor

As an option, you can order the sold separately CO2 injection port (Ca Reactor Feed/Injection Assembly) to send excess CO2 from your calcium reactor right into the ARID C30, which further benefits the growth of macroalgae. This unit includes quick disconnect fittings.

Manufacturer Info

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.

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