A media reactor is an aquarium filtration device that contains filter media. It helps to increase the effectiveness of the filter media inside by forcing all water that enters the reactor to come in contact with the media. This eliminates the problem of only exposing your aquarium water to a portion of the filter media—which is what happens when media is placed inside a media bag.

This is a drawing of a classic up-flow style media reactor.  While there are various different styles of media reactors that don't work exactly like what you see drawn here (including the BRS reactor), they all employ the same concept and provide the same benefits to tank owners. Most importantly, giving you a longer contact time with filter media to increase effectiveness.

Filter Media Reactor

In a fluidized media reactor, water is actively forced through the inlet via a small submersible pump or can be plumbed off the return line to your aquarium. Water then travels down the center inlet pipe to the bottom of the reactor where it is dispersed via a plate or grill. The dispersed water then travels up through your filter media which ensures the water comes into contact with the entirety of the filter media.

Media 1

The contact time with the filter media can easily be adjusted by controlling the water flow rate into the reactor via a ball valve. Slower flow rates result in longer contact time with the media and higher flow rates result in shorter contact time with the media.The ideal rate of flow is based on the particular filter media being used inside the reactor.

  • Carbon: Very slow flow rate with no tumbling of the filter media results in maximum contact time with the carbon ensuring all possible contaminants are removed. Carbon is soft so if tumbled it will break down into very fine particles and escape the reactor.
  • GFO: Moderate flow rate to create a slight and slow tumble of the media. This helps to expose the water to each and every particle of GFO and prevent any sort of channeling that may occur through the reactor. GFO is heavier and denser than carbon but too much water flow can still have the same effect as carbon where the media breaks down into fine particles and escapes the reactor.
  • BioPellets: High flow low rate to aggressively tumble the pellets inside the reactor. This helps the media to shed the bio-film created by the bacteria growing inside the reactor. The surplus of bacteria is consumed by filter and suspension feeding organisms, such as sponges and corals, or skimmed off by a protein skimmer toimmobilize nitrate and phosphate. NOTE: SPONGES SHOULD NOT BE USED INSIDE THE REACTOR WHEN USING BIOPELLETS.

After passing through your filter media of choice, the water then rises to the top of the reactor and exits through the outlet water line and is returned back into your aquarium or sump filtration system.