A media reactor is a chamber that holds loose filter media, such as granular ferric oxide (GFO), activated carbon or bio-pellets, and pushes aquarium water through it in a steady flow. Reef and planted tank keepers use them so the media is used evenly rather than sitting in a bag. The units differ in capacity, how they mount and whether a pump is included.
The six reactors below range from a palm-sized nano model to a 2 liter modular body. All figures come from each product page on Amazon.com. We have not used these reactors ourselves, so performance and tank-size claims are the makers’ own, and we call out listing numbers that look wrong.
As an Amazon Associate we earn from qualifying purchases. Links below are affiliate links, and they do not change the product information we give.
What to Look For
| Feature | Why it matters |
|---|---|
| Media capacity | Listed in grams, milliliters or liters of media |
| Tank size range | Makers name the aquarium volume each model suits |
| Pump | Some reactors include one; others need a separate pump |
| Mounting | Hang-on, sump, below the tank or on the side |
| Flow | Recommended flow is given per model; see the notes on units |
Specs at a Glance
| Reactor | Media capacity | Tank size (maker) | Pump | Notes |
|---|---|---|---|---|
| Two Little Fishies Little Reactor | 75 g (145 ml) PhosBan; 150 ml carbon | Up to 75 gal | Not included | About 20 GPH flow; 7 in cube |
| Two Little Fishies PhosBan 550 | 750 g (1.25 L) PhosBan | Up to 600 gal | Not included | 20 to 40 GPH flow; ball valve |
| Nyos TORQ G2 Body 2.0L | 2,000 ml, dual chamber | Larger reef systems | Not included | Twist-lock lid; micro-screen |
| Lifegard Medium Turbo | Not stated | Small and large tanks | Not included | 5 x 5 x 16 in; 3 lb; flow control |
| Aquatop MR-30 | Not stated | Sump or hang-on | SWP-360 included | 152 GPH; 6.5 x 5.5 x 23.5 in |
| Aquatop MR-20 | Not stated | Sump or hang-on | SWP-230 included | 95 GPH; 1-year warranty |
The 6 Best Aquarium Media Reactors
1. Two Little Fishies Little Reactor Nano
A compact upflow reactor that the maker says suits aquariums up to 75 gallons and fits nano and frag tanks. It holds up to 75 grams (145 ml) of PhosBan or up to 150 ml of activated carbon, with a recommended flow of roughly 20 gallons per hour, and can mount on the tank or below it. It measures 7.01 inches per side. The overview shows a maximum flow rate of 20 gpm and an item weight of 75 g, which look like unit and field slips, so go by the bullet points.
Suits: small tanks with limited space. Strengths: a compact body and two media options. Weaknesses: small media capacity and no pump. Skip it if your tank is large.
View Two Little Fishies Little Reactor Nano on Amazon
2. Two Little Fishies PhosBan Reactor 550
The largest reactor in this group by the maker’s figures: it says one unit suits aquariums up to 600 gallons and holds up to 750 grams (1.25 L) of PhosBan with a maximum recommended media height of 8 inches. The listed flow is about 20 to 40 gallons per hour, it hangs on the back of a tank or sits below it, and it includes a ball valve and fittings that rotate 180 degrees. The details table shows a size of 0.02 inches and a weight of 0.32 ounces, which cannot be correct.
Suits: large systems. Strengths: a large media capacity and a ball valve. Weaknesses: no pump and unusable size entries. Skip it if you want an included pump.
View Two Little Fishies PhosBan Reactor 550 on Amazon
3. Nyos TORQ G2 Body 2.0L Media Reactor
A modular dual-chamber reactor body with 2,000 ml of media capacity, model T-2498. Nyos says a chamber divider lets it run two media at once, a twist-lock system allows tool-free media changes and an included micro-screen keeps fine media in place. It is described as compatible with the TORQ G2 and G1 Dock. The page lists a first-available date of April 29, 2026, a weight of 2.41 pounds and package dimensions of 19.29 by 7.87 by 6.1 inches.
Suits: a large reef with two media types. Strengths: a dual chamber and a micro-screen. Weaknesses: a recent listing and a modular system that may need other parts. Skip it if you want one all-in-one box.
View Nyos TORQ G2 Body 2.0L Media Reactor on Amazon
4. Lifegard Medium Side Flow Turbo Reactor
Model R800128, described by Lifegard as a side flow reactor for bio-pellets, GFO and carbon with ceramic bearings and built-in flow control. The maker says it does not need PVC pipes, ball valves or flexible tubes. It measures 5 by 5 by 16 inches and weighs 3 pounds. The page lists no media capacity or tank size range, and its category rank sits under air pump accessories, so confirm what ships.
Suits: compact side-flow plumbing. Strengths: flow control and ceramic bearings. Weaknesses: no capacity listed. Skip it if you need stated media volume.
View Lifegard Medium Side Flow Turbo Reactor on Amazon
5. Aquatop MR-30 Media Reactor
An up-flow reactor with an acrylic chamber and a recessed O-ring lid, sold with an SWP-360 submersible pump, tubing, a tank hook and suction cups for sump or hang-on use. The title lists 152 GPH and the page lists 6.5 by 5.5 by 23.5 inches and 3.5 pounds. The overview gives the flow as 152 gpm, which is a unit slip, and the details show no warranty.
Suits: a pump-included setup. Strengths: a pump and mounting parts in the box. Weaknesses: no warranty on the page and no media capacity. Skip it if you want a warranty.
View Aquatop MR-30 Media Reactor on Amazon
6. Aquatop MR-20 Media Reactor
The smaller sibling, listed in its title at 95 GPH, with an SWP-230 submersible pump, intake and output tubing, suction cups and a tank hook. The overview lists a 3.5 by 2.5 by 15 inch body and a 1-year manufacturer warranty. It also shows a weight of 4.54 g and a flow of 2 gpm, both of which look wrong, so treat those fields with caution.
Suits: small sumps or hang-on use. Strengths: a pump included and a 1-year warranty. Weaknesses: no media capacity and incorrect-looking fields. Skip it if you need a high-capacity reactor.
View Aquatop MR-20 Media Reactor on Amazon
Specs to Check Before Ordering
- Media capacity in grams or milliliters, where the listing gives it.
- The tank size range the maker states.
- Whether a pump is included, and its model.
- Mounting style for your sump or hang-on setup.
- Units for flow, since some pages mix up GPH and gpm.
For setup and media loading, follow the maker’s instructions.
Mistakes to Avoid
- Trusting a flow figure whose units contradict the title.
- Assuming a pump is included when it is not.
- Ignoring the listed media height limit.
- Buying a modular body without checking what other parts it needs.
Aquarium Media Reactor FAQ
What goes inside a media reactor?
The makers list GFO, activated carbon, bio-pellets and phosphate sponges, depending on the model.
Do these include a pump?
Only the two Aquatop models list one. The others rely on a pump you supply.
The Short Version
For a nano tank, the Little Reactor. For large systems, the PhosBan 550. For two media in one body, the TORQ G2. For side-flow plumbing, the Lifegard. For a pump-included unit, the Aquatop MR-30. For a smaller pump-included unit, the Aquatop MR-20.
