To maintain pristine water quality in our aquariums, hobbyists often utilize carbon, ferric oxide media (like ROWAphos and Phosban) and/or other filter media to absorb dissolved organics and other chemicals from the water.

There are many ways you can add media to your aquarium. One of the best ways is by using a fluidized bed filter (FBF). Fluidized bed filters are commonly referred to as phosphate or media reactors.

Perhaps you've been wondering what a media reactor is and how they work. This article is for you.

They say a picture is worth a thousand words. To save you some serious reading, I've included an up-close photograph of Two Little Fishies Phosban Reactor 150.

Two Little Fishies Phosban Reator 150

Two Little Fishies Phosban Reactor 150: Inlet & Outlet

You'll notice two hose barb fittings at the top of the reactor, these are the inlet and an outlet. Water is pumped into the media reactors inlet through flexible tubing attached to a small powerhead. The inlet is connected to a center tube that carries water down to the bottom of the reactor. Water then flows upward through the media—allowing it to move and become "fluid"—before exiting through the outlet.

Seems simple enough, right? Good, because it really is that easy. The advantages of these filters are that they are not only effective, but easy to setup and maintain.

If you're wondering why using a fluidized filter might be better than simply placing a filter media bag inside a canister or other like-minded filter, we have the answer.

Water travels the path of least resistance when flowing through a filter. As detritus inevitably begins to clog the media within a canister filter, the water will start "channeling" around the clogged area(s) and only come into contact with a portion of the filter media. The media inside a fluidized bed filter, on the other hand, is constantly churned within the reactor. This prevents channeling and allows greater contact time between the water and filter media.

The items you'll need to setup your own media reactor include:

  1. A media reactor
  2. Filter media
    Carbon and phosphate media are among the most popular varieties.
  3. Powerhead/Water Pump
    Your media reactor may include a pump. Be sure to read the product description carefully before buying to determine if you'll need to purchase one separately. If your reactor does not include a ball valve to adjust water flow, I recommend purchasing a feed pump with adjustable flow so you can dial in the proper flow rate.
  4. Flexible tubing and hose clamps

For my setup demonstration, I am using Two Little Fishies Phosban Reactor 150, Aquarium Systems Mini Jet 606 Powerhead and Two Little Fishies HydroCarbon2.

The first thing you'll need to do is decide where you will place your reactor. I am hanging the reactor in this demonstration on the side of a sump.

Reactor Hanging on the Sump

Reactor with Tubing and Pump Connected

Next up: find a suitable location for your feed pump. Once you've chosen a spot, cut an appropriate length of tubing to connect the pump to the reactor. Remember to measure twice, cut once. You may also cut a piece of tubing for your exit line.

Since I've decided to place the pump in the bottom of my sump, I will cut 1 ½ to 2 feet of tubing to connect the pump to the reactor. The TLF Phosban Reactor I'm using includes a ball valve I will add between the pump and the filter. The instructions included with the reactor mention this, so I will reiterate: do not restrict the flow exiting the reactor. The pressure that builds up can cause leaks.

If the products you're using to setup your media reactor are new, you may want to give them a good rinse at this point to remove any dust, glue or residual debris that may have settled during the manufacturing process.

Rinse your filter media as well, per manufacturer guidelines. Instructions may differ slightly from manufacturer to manufacturer; free to contact us if you have questions.

It's time to add carbon to the reactor. But before you can place the media inside, you'll need to remove the top plate/sponge. Plug or cap the center tube— a piece of tape will suffice—to prevent media from falling down it. I actually used a strainer from an old Maxi-Jet Powerhead.

Fill the reactor chamber halfway with carbon. You really can't overdue it with carbon, so don't worry about adding an exact amount. Personally, I'd rather have too much carbon than too little. However, when I use phosphate media, I always adhere to the manufacturer's recommendations.

Adding Carbon to the Reactor

Reactor Half Full with Carbon Media

After filling the reactor chamber halfway with carbon, remove the cap you placed on the center tube and replace the top plate/sponge and fasten the lid.

Place or hang the feed pump inside your sump with the tubing attached. Then connect the tubing to your reactor. The outlet drain line will also need to feed back into the sump (or tank). I try to pull water from one side of the sump (where the water enters the sump from the tank) and drain it near the systems main return pump.

Assembled Reactor

Reactor Ready to Go

You are ready to turn the pump on. There may be some dust leftover even after rinsing the media, but this isn't a big cause for concern. Just slow the flow down after plugging the pump in to limit dust and media from entering your aquarium.

Once the water inside the reactor has cleared, you can fine-tune the water flow inside the chamber. Ideally you'll want to see a bubbling or boiling-type action at the top section of the media.

Congratulations! You have successfully setup a media reactor.

Fluidized Reactor in Action

"Can I mix different types of media within the same reactor?"

This is one of the most common questions aquarium hobbyists have about media reactors so I felt I should share my opinion on the subject.

I believe you are better off running multiple reactors than mixing different types of filter media together in the same reactor. You may alternate media types—running one type for a month and then switching to another.

The reason I don't think media types should be mixed within a single reactor is because each type of media requires a different flow rate to maintain fluidization inside the filter.

Carbon usually requires a higher flow rate than phosphate media. If you run the filter with a slower flow rate for phosphate, you risk having carbon media settle at the bottom. This can cause channeling. If you set the flow rate higher to keep the carbon fluidized, you risk pushing the phosphate media right out of the reactor.

Also, depending on your waters chemistry, you may find the time between changing different media varies. For example, your carbon may need to be replaced every 2-4 weeks whereas your phosphate media may not need to be changed for 6-8 weeks.

Risks aside, it is doable. Bear in mind you'll need to carefully observe your media and flow rate to prevent the aforementioned problems.

Another frequently asked question: "Are all media types safe to use inside a media reactor?"

The answer is, unfortunately, no. Some types of filter media just don't do well in the fluidized environment. Fluidizing some types of media will cause them to break down and crumble into a fine dust. Other types are either too large or too small. When in doubt, give us a shout! We'll be happy to let you know if the media you have in mind is suitable for a fluidized bed filter.

Media reactors are fairly simple pieces of equipment that can dramatically improve the water quality of your aquarium. Whether you run carbon, phosphate or another type of media, as long as you follow best practices, you should begin to see improved water quality and clarity in no time.