DIY Carbon & GFO Filters for BioCubes

Back in the day, I had an Oceanic BioCube 8g aquarium.  Although I loved the aquarium, there wasn’t enough room for a skimmer or any sort of carbon/GFO removal product.  Needless to say, the aquarium had a constant problem with algae.

I came up with this simple DIY project to help combat the algae problem.  Basic sewing skills are required.


  • 1/4 yard polyester felt from the fabric store
  • Sewing thread in 2 colors (preferably brown and black)
  • Sewing machine or sewing needle
  • GFO and/or carbon
  • Sheet of paper & a pen/pencil
  • Scissors


1.  Using the pen/pencil and paper, trace the outline of the BioCube filter section to make a pattern.  Cut out the pattern.

BioCube 8 Filter Pattern

2.  Lay the pattern on a double thickness of the filter floss material.  Cut out the pattern.

Cut Fabric According to Pattern

3.  Thread the needle (and bobbin if using a sewing machine) with the appropriate color thread.  I use black for carbon filters, brown for GFO filters, and both colors for a mixed filter.

Brown & Black Thread for Carbon & GFO

4.  Stitch around the filter, but leave a small opening to add the media later.

Stitch the Filter

Leave a Small Opening

5.  Fill the filter full of carbon, GFO, or a mixture of both.  Keep in mind that a GFO filter will need more regular changing than a carbon filter.

6.  Sew the opening closed.

Sew Granules in to the Filter

7.  The filter is finished.  Gently rinse it in RO/DI water to remove small particulates of carbon/GFO.  Place it into the filter slot!

Filter installed


1.  I used a polyester felt from the fabric store.  If you find the filter gets clogged too fast, then look for a more open-mesh felt.  Obviously, if it isn’t clogging up fast enough, then use a thick, tight-mesh felt.

2.  Use only the pure white felt as the colored felts contain dyes that may be harmful to aquatic inhabitants.

3.  These are disposable – they are not meant to be reused.

4.  I ran one carbon filter for three weeks per month.  I ran one GFO filter for the remainder of the month.  Adjust filter run times for your application.

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