DIY Carbon Tube Filtration System

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The concept of the Carbon Tube Filtration System is really quite simple. The Tri Base Pelletized Carbon (TBPC) is put into a PVC tube through which a high volume of tank water is pumped after it has been mechanically filtered. Right Now Bacteria (RN) is an aerobic bacterial compound, which means it "lives by oxygen supply".

When picking your mechanical filter and pump, you want water flow through the carbon tubes that will turn over the tank water at a rate of six to 10 times per hour. Do not forget to take into factor that the flow rate will be slower than what the filter instructions say due to the water flow through the carbon tubes. Once the aquarium water passes through the canister filter and the carbon tubes, the water is returned to the tank free of Nitrogen wastes.

For Smaller Aquariums Under 55 Gallons 

For smaller aquariums, under 55 gallons a Magnum 350, Eheim, Fluval, or similar pump works well. These canister filters act as both your mechanical pre-filter and water pump in one unit. For tanks that are in the range of about 75 gallons, you can choose to use two Magnum 350's (for example), each one with one carbon tube attached.

For Aquariums Over 75 Gallons 

If your tank is over 75 gallons you will want to go to a larger capacity water pump with a separate canister filter to use as a mechanical pre-filter to help remove debris that can clog the TBPC making it less efficient. The Mag Drive, Little Giant, Iwaki, and Rainbow make pumps in the range of 1000 to 1800 gallons per hour. There are a number of mechanical filters, like Ocean Clear, on the market which can be used as a pre-filter.

The following is our interpretation of Dave's "Theory of Carbon Tube Filtration", with a couple of extra features with associated benefits Dave never got around to putting on paper.

DIY Carbon Tube Filter Material List

The PVC tubes can be of any diameter you wish. Keep in mind 10 pounds of TBPC occupies 0.35 cubic feet. 87 inches of three-inch PVC or 49 inches of four-inch PVC will hold 10 pounds of TBPC. Hiatt Distributors Limited recommends 0.1667 pounds of TBPC for each gallon of tank water for the best results. Our customers have great results with somewhat less, but then again, more TBPC means faster cycle time and more fish in your tank, to a point.​

DIY Carbon Tube Filter Material List
The Spruce / Stan & Debbie Hauter

Materials You'll Need

  • 10-foot length of 4-inch thin wall ABS
  • Four ABS Slip end caps
  • Four 5/8" barbs, male thread x barb (or larger, depending on your pump hose size)
  • 10-foot length of 5/8 I.D (or larger, depending on your pump hose size) clear reinforced plastic tubing (So it will not twist and kink).
  • Four stainless steel hose clamps or 6" wire ties
  • One sheet of white egg crate (The stuff used for covering on ceiling lighting. Check the lighting department at stores.)
  • Four 4" x 4" pieces of fiberglass or plastic window screen
  • One roll of PINK plumber's Tape (It is the thickest tape on the market)
  • One drill, one tap, and ABS Glue

If you have a few challenges finding some of the same materials here, be sure to research the additional tips for construction. It's also important to understand how to pre-flush the carbon tubes to remove possible carbon residue, what you can do if you encounter leakage and a few other helpful tips. 

DIY Carbon Tube Filter Construction

  1. Cut two 28" pieces of the 4" ABS from the 10' length (this will hold approx. 10 lbs of TBPC).
  2. Drill and tap the correct holes in the end caps AND couplings for the 5/8" barbs.
  3. Screw-in the 5/8" barbs using the PINK plumber's tape around the threads.
  4. Using the inside of the coupling as a template, use a magic marker and mark the egg crate. Cut the piece with a jigsaw (or a pair of diagonal cutters).
  5. Using a hot glue gun (or silicone caulking), glue the window screen along the egg crate lines. Cut off the excess window screen.
  6. Slide the egg crate flush inside the pipe end cap. Hot glue the egg crate in place.
  7. Glue the end cap to the pipe. Very important: Do this only on one end so you can open and clean the tube from the other end.
  8. Glue the coupling (with another piece of egg crate in it) to the other end. Allow drying outside for a day to vent the fumes from the solvent.
  9. "Fizz off" the TBPC in a bucket of freshwater, then rinse thoroughly to remove the "fines".
  10. Fill the tube tightly with TBPC.
  11. When screwing the end cap on, put PINK plumber's tape on the edges. This thick tape will eliminate leakage.​
  12. Cut 12" of the plastic 5/8" tubing and hook the two tubes together. Clamp the ends with the stainless steel clamps or the wire ties.
  13. Hook the tubes to your pump. A high flow of at least six to 10 times an hour is excellent. Remember the exhaust part of the tube is where the egg crate is installed. The flow must be in that direction, otherwise, the TBPC might infiltrate down the lines and enter the aquarium.

If the tubes are tightly filled with the TBPC, they can be horizontal. If they are loosely packed, they must be vertical (with downward water flow). The shape of the TBPC doesn't allow it to pack, so you can fill the tubes with as much as you desire.

Starting the Carbon Tube

Turn on your tank and allowed it to run with the carbon tubes. Begin acclimating one to three fish that you are going to place in the tank by using the airline drip method. That is, siphoning the water from the tank to the bucket where the fish are at a drip, drip, drip-rate. You'll want to add some AmQuel or another type of ammonia buffer to the bucket water to ensure the fish do not get ammonia burn. This usually takes an hour. The fish acclimate slowly to the water change. Turn off any skimmers or UV filters that you have in the tank. Remove the cartridge from the mechanical filter. Five minutes before introducing the fish, add water from your tank to the bottle of Right Now, shake up, and pour in. Rinse the bottle of any remaining bacteria. Then put your Light load of one to three fish in your tank and let it run. Your tank will cloud for the first 24 hours, then it will be crystal clear. After 24 hours, put the cartridge back in the mechanical filter. The next day, the readings should be "0", "0", "0". You can add another fish every 5 to 7 days until your tank is where you want it.

If you want to "tweak" your tank, add another tube to the chain and put Hiatt's pH Adjustment Rock and Metal Gone (MG) in it. MG is used to eliminate or avoid any hair-micro algae problems

Carbon Tube Maintenance and Tank Cleaning

Maintenance is a breeze. Clean or change your mechanical filter cartridge once a week (more if needed) and vacuum siphon and clean your substrate once a week. The Magnum brand filter has an attachable Power Kleen Gravel Washer specifically for this purpose. Just unhook the Magnum intake hose, attach the gravel washer and "vacuum" the bottom of the tank. Shut off the Magnum, replace the cartridge (keep two, one for in the filter and one for rotating), hook the intake hose back up and turn it on again. Clean the extra cartridge and hang it out to dry until the next "maintenance" spat.

After a period of time, the carbon can start to compact. It needs to be loosened up so that the proper water flow through the carbon is allowed. If the carbon becomes compacted and clogged, this may allow for anaerobic bacteria to grow, which you do not want. At least once a month during a routine water change just backflush the carbon tubes. Hiatt strongly recommends back flushing the carbon tubes for no more than 10 to 15 seconds. 

The greatest benefit of this system is that it is so easy and inexpensive to modify, add on to, reduce your filtration system and finally have the complete Nitrogen Cycle. No need to buy skimmers or any other "do-holly's" to get an effect, unless you choose to add them. No doubt you already have the pump and a bunch of extra tubes laying around. Just mix and match to your heart's content.

One of the greatest things about this hobby is that everyone can be a "research scientist", doing their own experiments, using their imaginations to attempt proving a theory. And, make sure that you keep a tank log. Use the Aquarium Manager Program or a similar computer program.

Additional Construction Notes

  • Can't get ASB tube material, or think that thin wall PVC will work just a well or better? Solution: Go ahead and use PVC, it's lighter and cheaper.
  • After washing and "fizzing off" the carbon there still may be some black/gray residue coming out of the tubes. Solution: Take a garden hose (do this outside) and let the water flush through the tubes to help remove any residue. This also allows testing for leaks.
  • Don't have the right size "tap" for the male hose fitting hole in the end cap? Solution: Use a regular drill bit, stick connectors into snug holes and use JB Weld around the outside of holes and connectors to secure and seal. Let dry and cure overnight.
  • Do the end caps leak using plumber's tape? Solution: Glue on all end caps.
  • What if even after gluing end caps on you still get some leakage? Solution: Dab more PVC glue around the outside seam of end caps.
  • Do your fish appear stressed for oxygen? Solution: Add a couple of airstones to help with vertical water movement in the tank and aid in the oxygen/carbon dioxide gas exchange that takes place on the water surface.
  • What if your magnum filters the water well, but you need more circulation and water movement in the tank? Solution: Mount a powerhead (or two) on the opposite end of the tank from where the carbon tube outflow returns.

DIY Carbon Tube

Here is a constructed DIY carbon tube and it's associated stand. This tube was built from 4" PVC and is to be used vertically. You can see the stand for the carbon tube in front of the tube.

DIY Carbon Tube
The Spruce / Stan Hauter