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DIY: Rubbermaid Bio-Filter

Bio-filters provide a healthy and ecologically sound way to regulate your fish tank or pond water. They work by running the water over porous material on which bacteria live. The bacteria consume the waste material in the dirty water and convert it into a substance usable by plants. At this point it is still hazardous for fish. Before it returns to the tank it should be run through a bed of plant roots to remove the last of the hazardous chemicals. This system is known as a hydroponic filtration system, biological filter or bio-filter.

Things You'll Need

Rubbermaid bucket
Deep Rubbermaid tray
Rubber cement
2 yards of 3/4-inch tube
Drill with 3/4-inch bit
Perlite or vermiculite
Soil
Colander
Sponge
Seeds
Boiling water

Instructions

- 1
  
  The bucket should preferably be Rubbermaid, to avoid rusting, but treated wood or metal can also be substituted.
  
  Drill two holes on the side of the Rubbermaid bucket or bin, one hole most of the way toward the bottom and one hole most of the way toward the top. Make sure your drill bit matches the size of the tubes you will use. Upend your container to make sure no shavings remain inside.
- 2
  Attach the tubes. Use the rubber cement to secure them, and give them several hours to a day to dry out. The tubes you attach should be at least a yard in length each, one to reach the pump and the other to reach the next container.
- 3
  Drill the same size hole in one end of your eventual plant box (the Rubbermaid tray). Follow the same procedure to make sure that no shavings are left over.
- 4
  
  The drill bit must be an appropriate size, or you will have to start over or seal the holes.
  
  Drill additional holes in the far end of the plant box from the first hole. These should be smaller, no more than a few millimeters wide, but large in number and spread out along the one end.
- 5
  Attach the end of the tube already attached to the bottom of the bucket to the single large hole in the box. Seal it similarly, using rubber cement. Let it sit for a day before you attempt to move it.
- 6
  Rinse all the rocks and substrate you'll be using. Lava rocks need to be soaked and rinsed several times to remove all the dust. Perlite, vermiculite and dirt just need a single quick rinse in a colander.
- 7
  Place the lava rocks in the bucket. The level of the rocks should reach just above the halfway point. Make sure the rocks are all of approximately equal size so that none will move to the bottom and clog the system.
- 8
  
  Potting soil, not topsoil, should be used for this project. Topsoil is weak in nutrients and is poor quality for growing plants, despite costing less.
  
  Put down the perlite or vermiculite in a thick layer -- up to an inch deep -- in the bottom of the plant tray. Put the dirt on top of it in an equally thick layer.
- 9
  Put the plant tray on the upper edge of your tank, facing so that the small holes in one end are over the water. Put the bucket with the lava rocks slightly above this height. You may need to employ a ladder or stand for this purpose.
- 10
  Pour water over the plant tray to settle and moisten the substrate. If any of the perlite or vermiculite falls through the small holes, put a thin layer of sponge over them.
- 11
  Attach the top tube of the lava rock bucket to the water pump. You should need no rubber cement this time. If the tube doesn't fit over the end of the output of the pump, try soaking it briefly in boiling water.
- 12
  Plant the seeds of a lush-growing plant in the plant tray. The plants will take several weeks to get started. These plants should also not be tall, just lush. Something like lettuce will do fine.
- 13
  Put the pump in the water and turn it on. Do not do this with fish in your tank. Start the filter several weeks before you plan to put in fish, to allow the bacteria to colonize in the lava rocks and the plants to begin to grow.

Animals & Science