Pax Bellum

A.R.I.D. C36 Macroalgae Reactor (300-1000 Gal. Sys.)

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$2,025.00 $2,025.00

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A Quantum Leap in Nutrient Management

The A.R.I.D (Algae Remediation Illuminated Device) Reactors bring macroalgae culture into the modern era of reefkeeping, incorporating highly refined, elegant design and innovative technology for a macroalgae reactor unlike any other. This ingenious device utilizes macroalgae (specifically Chaetomorpha) to function as a tunable nutrient export mechanism. The ARID reactor is the original, patented macroalgae reactor from Pax Bellum, and they are the gold standard that others seek to emulate.


When used as recommended, organic wastes and nutrients can be maintained at optimal levels, preventing algae outbreaks that could lead to frustration and even tank shut-down. By limiting availability of nitrogen and phosphorus in the system, algae and similar pest organisms have a very difficult time even gaining a foothold. The ARID reactor is so effective that it can often become necessary to begin supplementing certain nutrients into the system to maintain basic levels necessary for metabolic functions in the reef


More Than Simple Nutrient Control

The tube and flange design of the device serves to isolate the algae from atmospheric CO2, which effectively limits the carbon source for the algae to only that which is contained within the aquarium water. This is a self-regulating feature and eliminates organic carbon buildup (yellowing of the water). The ARID could be thought of as a lung for the aquarium, with the macroalgae exchanging pH-depressing CO2 for life-giving oxygen.


Use the ARID with the Triton Method

One of the reasons we love this product is due to the fact that it satisfies the need for the algae component when running the Triton Method. This method relies heavily on algae as the heart of the filtration system. Nutrients, namely No3 and Po4 are largely kept in check by an algae component roughly 15-20% of the system volume. For aquarists that currently lack the space or ability to incorporate a large algae filter in their existing or new setup, this upright, sealed unit offers an excellent alternative. Because of the fast growing nature of Chaetomorpha algae especially in this reactor, we recommend placing it in the upper half, if placing other algae in the same unit.


Use the ARID with a Calcium Reactor

The Calcium Reactor Feed & Injection Assembly can be purchased separately to allow use with your calcium reactor. It is a compact manifold that threads directly into the water inlet on the base of the ARID C36, allowing the ARID reactors to be used downstream from a Calcium Reactor (CaRx). By utilizing the ARID reactor inline with your calcium reactor, you gain a synergistic benefit. The ARID reactor removes excess CO2 from the effluent, mitigating the pH-lowering effects of the CaRx on your reef tank, and the macroalgae benefits from a constant CO2 source. This optional kit can increase the growth rate of your macroalgae and with it the nutrient uptake rate and dissolved oxygen production


Manufacturer Recommendations

Pax Bellum recommends running the ARID on a reverse daylight cycle (i.e.; opposite of the display aquarium) which helps to balance the natural day/night pH swing that occurs, and to maintain high dissolved oxygen levels throughout the night when the display aquarium lighting is off and photosynthesis has ceased.


The ARID is capable of targeting specific nutrient(s) for export. In the reef aquarium, the main concern is balancing the nutrients nitrogen, phosphorus, potassium, and carbon (N:P:K:C), with the goal of limiting phosphate (P). Usually never in short supply, potassium (K) and carbon (C) are not dosed. However, nitrogen (N) can become depleted rapidly by the growth of algae, causing growth to stall. To keep the algae growing, the aquarist should dose the, Nitrogen+Molybdenum solution that comes with the ARID reactor, as needed to maintain the ratio of NO3 to PO4 at a minimum of 20:1 and ideally at 100:1 (example; 3ppm NO3 to 0.03ppm PO4). Maintaining this ratio will allow the Chaetomorpha or macroalgae of choice to continue to grow until phosphate levels reach the minimum cut off for growth at 0.02ppm.



  • Recommended Aquarium Size: 300-1000 US gal. 
  • Recommended Flow Rate: 600-1000 gph 
  • Light source: Coaxial LED light tube
  • Chamber Material: PVC
  • Footprint: 13" x 12" 
  • Height: 36"
  • Inlet/Outlet port size: 1" FNPT 
  • Power consumption: 42 Watts  @ 120 VAC, 60 hz

Note: Algae and pump not included. CaRx Feed & Injection Assembly sold separately.


What's Included?

  • ARID C36 Macroalgae Reactor
  • Coaxial LED Light Tube Assembly
  • Diffuser Discs
  • Power Supply
  • 250 mL Fe+Mn Supplement
  • 1 L N+Mo Supplement
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