An Aquamaxx algae reactor is a sealed chamber that grows macroalgae inside your filtration system, using the algae's natural nutrient uptake to remove nitrates and phosphates from your reef tank water. Rather than sending algae to a separate refugium, the reactor keeps it contained, illuminated, and tumbling in a controlled flow so you get maximum nutrient export in a small footprint. If you are fighting persistently high nitrates in a reef tank and do not have space for a traditional refugium, this is one of the more effective solutions available.
This article covers how Aquamaxx algae reactors work mechanically, the specific models they make, what macroalgae species work best, how to set one up, and how it compares to other nutrient export methods. You will also find honest information about what it cannot do, so you do not buy one expecting a miracle.
How an Algae Reactor Works
The core idea is straightforward. Macroalgae like chaetomorpha or gracilaria absorbs ammonia, nitrate, and phosphate as it grows. When you harvest the algae regularly, you physically remove those nutrients from the system. An algae reactor speeds this up by creating optimal conditions for rapid algae growth inside a compact, sealed housing.
The Aquamaxx reactor works by pumping sump water into the bottom of the chamber. The water tumbles the algae mass continuously, which prevents it from compacting and ensures every part of the algae gets light and nutrient exposure. An internal LED light runs on a reverse photoperiod, meaning it is on when your display tank lights are off. This stabilizes pH by adding oxygen to the water at night when corals would otherwise cause a pH dip through respiration.
What Makes a Reactor Different from a Refugium
A traditional refugium is an open chamber, usually a section of your sump or a hanging-on-tank box, with a light above it. It works well but has drawbacks. Chaeto in a refugium can compact into a ball where the interior gets no light or water flow, reducing growth. Light escape annoys people and disrupts the sleep environment. A reactor solves both problems: it is sealed so no light escapes, and the tumbling action keeps the algae actively growing throughout the mass.
Reactors also tend to produce more nutrient export per liter of space compared to passive refugium setups because growth rates are higher with consistent flow and 24-hour light coverage.
Aquamaxx Algae Reactor Models
Aquamaxx makes two primary reactor models that differ mainly in capacity.
Aquamaxx FR-SE-1 Algae Reactor
The FR-SE-1 is built for tanks in the 30-100 gallon range. It measures approximately 5 inches in diameter and 12 inches tall, with a total height around 18 inches including fittings. The internal LED is tunable across a red and blue spectrum, which is what algae actually uses for photosynthesis. Green light does almost nothing for algae growth, so the targeted spectrum here is a real advantage over slapping a random light above a refugium bucket.
Flow rate recommendation for the FR-SE-1 is roughly 50-100 gallons per hour. Too slow and the algae will not tumble properly. Too fast and the algae gets compressed against the top of the chamber.
Aquamaxx FR-SE-2 Algae Reactor
The FR-SE-2 is the larger version, suited for tanks from 75 to 200+ gallons. It has a wider chamber at around 6.5 inches diameter and holds significantly more algae mass. The LED is the same tunable design but more powerful to penetrate the denser algae ball. Flow rate requirements scale up to 100-200 gallons per hour.
Both models use standard 3/8-inch tubing fittings and include a ball valve for flow adjustment. They require a small pump to push water through the reactor. Most people use a small powerhead or pull water from their return pump with a dedicated branch line.
Best Macroalgae for Aquamaxx Reactors
Not every macroalgae species works equally well in a reactor. The tumbling action favors species with a loosely structured growth form.
Chaetomorpha (Chaeto)
Chaeto is the standard choice and the one most people use. It grows as a tangled green mass, tumbles freely, and tolerates the constant water flow well. It is also extremely robust. You can let the growth run large and harvest aggressively without killing the colony. Nutrient uptake rates are good, and it is readily available at local fish stores or through hobbyist swap groups.
The one downside is that chaeto can compact if the flow rate is too low. Watch for it forming a tight ball against one side of the chamber. If that happens, increase flow slightly.
Gracilaria
Gracilaria is a red macroalgae with excellent nutrient uptake and a bonus benefit: it is edible. Tangs and other herbivorous fish absolutely love it. You can harvest from the reactor and feed it directly to your fish as a supplement. Growth rate in a reactor is slightly slower than chaeto in my experience, but the fish-food value makes it worthwhile for some setups.
Ulva
Ulva (sea lettuce) works but is less common in reactors because it is more prone to fragmenting and passing through outflow screens into the main tank. If you run Ulva, use a fine mesh on the reactor outlet.
Setting Up the Aquamaxx Algae Reactor
Installation is not complicated but the details matter for performance.
Placement and Plumbing
Mount the reactor in your sump or beside it. The inlet pulls water from the sump and the outlet returns treated water. Position it so you can easily open the top cap for harvesting without disconnecting plumbing.
Use a dedicated small pump or a splitter on your return pump line. The key is getting flow in the correct range for your model. Install a ball valve on the inlet line to adjust flow. You will fine-tune this after starting the reactor and observing whether the algae tumbles freely.
Starting the Algae
Seed the reactor with a golf ball-sized clump of chaeto or gracilaria. Do not overfill it on day one. The algae needs room to grow. A reactor that is packed solid has no room for the growth you are trying to achieve.
Set the LED to 100% intensity on both channels to start. Some people dial this back once the reactor is established, but strong light encourages the rapid initial growth that establishes the colony.
Reverse Photoperiod Timing
Set the reactor light on a reverse photoperiod: on when your display lights are off, off during the day. This evens out the oxygen/CO2 balance in your system and prevents the pH swings that happen in reef tanks overnight. Typical setup is display lights on 8-12 hours, reactor light on during the remaining hours.
Harvesting
Harvest when the reactor is roughly three-quarters full. Remove the top cap, pull out a portion of the algae, and discard it (or feed it to your fish, or compost it). This is how you actually export nutrients. The algae contains the nitrates and phosphates it absorbed. If you never harvest, you are just temporarily storing those nutrients inside the reactor, not removing them.
Harvest frequency depends on growth rate, which depends on how nutrient-rich your water is. In a new tank with low nutrients, you might harvest once every 2-3 weeks. In a heavily stocked tank you might harvest weekly.
What an Algae Reactor Cannot Do
This is worth being direct about. An algae reactor is a nutrient export tool. It does not sterilize water, does not filter mechanical debris, does not remove fish waste directly. You still need mechanical filtration, a protein skimmer on a reef tank, and regular water changes.
Algae reactors also work on a delay. You add one to your system and nutrients start dropping over weeks, not days. If your nitrates are at 80 ppm, a reactor will bring them down, but it might take 4-6 weeks to see a significant reduction depending on your bioload and how aggressively you harvest.
They are not a replacement for good husbandry. Overfeeding, overstocking, and skipping water changes will overwhelm the reactor's capacity. Think of it as part of a complete nutrient management approach rather than a single solution.
For a complete picture of essential reef and freshwater equipment, the Best Aquarium Equipment roundup covers filtration systems, lighting, and circulation gear that work alongside a reactor setup.
Comparing Algae Reactors to Other Nutrient Export Methods
Protein Skimmer
A skimmer removes dissolved organic compounds before they break down into nitrate. A reactor removes nitrate that has already formed. They address different stages of the nitrogen cycle and work well together. Most reef keepers use both.
Macroalgae Refugium
A traditional refugium works on the same biological principle as a reactor. The reactor wins on footprint and light containment. The refugium wins on simplicity and lower cost, since it requires only a chamber and a light rather than a dedicated reactor unit.
Nitrate-Removing Media (GFO for Phosphate, Bio-Pellets for Nitrate)
GFO (granular ferric oxide) removes phosphate through adsorption. Bio-pellet reactors grow a bacterial biofilm that exports carbon and nitrate. These chemical/biological media work faster initially but require ongoing media replacement costs. An algae reactor is self-sustaining as long as the algae grows. Over 12-24 months, the reactor often costs less than regular media replacement.
The Top Aquarium Equipment page has more information on how various filtration approaches compare across different tank types.
FAQ
How long does it take for an Aquamaxx algae reactor to lower nitrates?
Expect 4-8 weeks to see meaningful reductions if your tank has elevated nitrates. Growth rate ramps up as the algae colony establishes. Many people report their nitrates dropping from 20-40 ppm to under 5 ppm within 6-8 weeks once the reactor is running well and they are harvesting consistently.
Do I still need a protein skimmer if I run an algae reactor?
Yes, on a reef tank. The skimmer handles dissolved organics before they convert to nitrate, while the reactor handles nitrate that has already formed. They address different points in the nutrient cycle. You can run a reactor-only system in some lightly stocked setups, but on a typical reef with corals and fish, a skimmer plus reactor is the standard combination.
How do I know if the flow rate is correct?
The algae should be tumbling continuously, rotating through the reactor chamber in a slow, loose motion. If it is sitting still and compacted, increase flow. If it is being shredded and tiny fragments are coming out the outlet, reduce flow. A slowly tumbling, freely moving mass is what you are aiming for.
Can I use an Aquamaxx algae reactor on a freshwater planted tank?
Technically yes, but it is unusual. Freshwater planted tanks typically manage nutrients through substrate fertilization and water changes, not through macroalgae export. Freshwater macroalgae options are limited. Most freshwater keepers who want natural nutrient export use a planted tank directly or a separate planted section of their filtration rather than a reactor.
Key Takeaways
The Aquamaxx FR-SE-1 handles tanks up to 100 gallons and the FR-SE-2 scales up to 200+ gallons. Chaeto is your best starting algae. Set the light on reverse photoperiod, get the flow rate right so the algae tumbles freely, and harvest consistently. Nutrient reduction takes weeks, not days, and the reactor works best as part of a complete filtration strategy rather than a standalone fix. If you have persistent nitrate and phosphate problems in a reef tank, this is a solid, low-maintenance long-term solution.