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MA Reactors

A Smarter DIY Media Reactor for Reef Hobbyists

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The MA Reactor is a cost-effective, DIY-friendly alternative to traditional off-the-shelf media reactors, designed for reef keepers who want performance, flexibility, and control without the premium price tag.

Built with simplicity and functionality in mind, the reactor is approximately 90% 3D-printed and requires only a PVC tube, rubber feet, and a compatible pump to complete the build.

Why Choose the MA Reactor?

Designed for DIY Hobbyists

Quick & Easy Media Changes

Unlike standard reactors with fixed or limited flow adjustment, the MA Reactor is designed to operate with a wavemaker. This provides extremely precise control over flow rate and allows you to take advantage of pulsing modes for improved media agitation and contact time.

Better control means:

  • Reduced channeling

  • More efficient filtration

  • Optimized performance across different media types

This reactor is designed for reef keepers who enjoy building and customizing their own equipment. Its modular design makes assembly straightforward while helping to keep costs down. You only need to supply:

  • A PVC tube

  • Rubber feet

  • A pump

Everything else is 3D-printed and purpose-built for the system.

The reaction chamber screws directly onto the base—no complicated clips, brackets, or full disassembly required.

Simply:

  1. Unscrew the chamber

  2. Remove and clean it

  3. Add fresh media

  4. Screw it back into place

Fast, simple, and maintenance-friendly.

Two Sizes Available

Designed for DIY Hobbyists

The media reactors use Jebao wavemakers—readily available and offering excellent value for money.

  • MLW-5 – Ideal for smaller tanks and lighter media loads

  • MLW-20 – Suitable for larger systems or higher media capacity

Choose the model that best matches your tank volume and filtration needs.

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Ideal for:

  • Carbon

  • GFO

  • Phosphate removers

  • Other common reactor media

This reactor is designed for reef keepers who enjoy building and customizing their own equipment. Its modular design makes assembly straightforward while keeping costs down. You supply:

  • A PVC tube

  • Rubber feet

  • A pump

Everything else is 3D-printed and purpose-built for the system.

Build Guide

Putting the media reactor together is a breeze. Here’s a guide to what’s needed:

Build Video..

In this video, we walk through the complete build process of the Marine Assistant Reactor. This guide will help you get your media reactor up and running smoothly.

Assembling the Reactor...

Step 1. Print (or Buy) the parts.

First, you’ll need to decide which reactor you would like to build. Here’s some information to help you make that decision.
Reactor For the MLW-5 pump (Mini)
​Reactor For the MLW-20 pump
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IMG_20260323_211021_edited.png
This reactor is very compact and is better suited to non-moving media due to its smaller, less powerful pump. It is perfect for activated carbon, for example. However, it will still tumble media as long as it is not overloaded and the settings are correctly adjusted.
This reactor has a larger reaction chamber than the Mini and is much better suited to tumbling media. It uses a larger (more expensive) pump, draws more power, but is also more capable than the Mini.
IMG_20260323_211153.jpg

The 3D print files are available here:

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You will need either a 90 mm PVC tube for the MLW-20 version or a 63 mm tube for the MLW-5 version.

Step 2. Assemble the Reaction Chamber
 
First, cut your tube to the required length. To do this, you will need to measure how deep the water is in your sump. Then add either 5cm fpr the MLW-20 or 3cm for the MLW-5 version, This is the length you will need to cut your tube to for either pump.
Once cut, you will need to glue on the bottom 3D-printed part as well as the top screw mount.
Apply CA glue around the inside of each part and press them onto either side of the tube.
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Apply even pressure on a flat surface to ensure the parts are seated correctly.
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The bottom is sealed, and the top is fitted with a lid to keep the media enclosed.
Step 3. Glue the lid together.

The lid of the reactor is made up of two parts and screws onto the top of the chamber. There is also a small grid piece that keeps the media inside the chamber.
It’s really simple to assemble. Apply some CA glue to each of the “pegs” on the underside of the lid, then attach the threaded ring.
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The ring has corresponding slots for the pegs to ensure correct alignment.
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Place the grid onto the top of the reaction chamber, then screw on the lid.
Step 4. Put the Pump in the Base

Depending on your reactor, you will need to install either the MLW-5 or MLW-20 into the body of the reactor.
The pump is inserted from the bottom of the body and secured with a small brace and a screw.
 
The pump is easily removable for maintenance.
 
On the bottom of the body, there are also holes for suction cups if desired.
A Couple of notes...
 

Flow tuning & performance

  • Start with lower pump power and gradually increase flow to find the sweet spot for your specific media.

  • Different media behaves very differently—carbon usually prefers gentle flow, while GFO often needs more agitation.

  • If you see channeling (water cutting straight paths through the media), reduce flow or add more media to improve contact time.
     

Maintenance

  • Rinse new media before adding it to reduce dust and initial clouding.

  • Clean the reactor regularly to prevent buildup that can restrict flow.

  • Inspect the pump periodically, especially if you’re running heavier media loads.

  • The reaction chamber screws onto the body. Do not overtighten it onto the pump housing.
     

Installation

  • Position the reactor where it is easy to access for refills and cleaning.

  • Make sure suction cups (if used) are fully pressed onto a clean surface for best grip.

  • Avoid placing the reactor where it could trap air or run partially dry.
     

Media usage

  • Don’t overfill the chamber—leaving a small gap improves flow and tumbling performance.

  • Mix media types cautiously; some combinations can compact or reduce efficiency.

  • Replace or refresh media in small batches rather than all at once for stability in your system.
     

Pump & wavemaker

  • Use pulsing modes sparingly at first until you understand how your media reacts.

  • Higher pulse intensity isn’t always better—it can reduce contact time in some setups.

  • If vibration is excessive, reduce power or check mounting stability.
     

Troubleshooting

  • If media isn’t moving, check for overfilling or insufficient pump power.

  • If fine media is escaping, ensure the grid is seated properly and not damaged.

  • If flow drops over time, the chamber or pump likely needs cleaning.

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