Internal Air Filter with Ceramic Media

Procedure to create filter:

 1) Drill a few holes in the top of a 1L bottle cap
    --> at least 5 holes
 2) Drill a hole in the neck of the bottle
 3) Drill a hole in the side of the bottle
 4) Drill several holes in the bottom of the bottle
 5) Insert a suction cup into the hole on the side of the bottle
 6) Fill bottle with biological media
 7) Place cap on bottle
 8) Insert an air hose into the side of the bottle neck 
 9) Cut a hole in an aquarium grade sponge so that the bottle cap goes halfway down the sponge
 10) Place bottle in aquarium, cap facing down
 11) Attach the other end of the air line tubing onto an air pump
 12) Turn on pump and begin running 

How it works:

 As air is pumped into the bottle the air will rise through the bottle causing suction behind it.
 Water is pulled through the sponge where it is mechanically filtered.
 Water goes through the bottle cap, as the air rises up through the media it is biologically filtered and released through the holes at the top where the water is fully filtered.   
 The bubbles that are rising hit the water surface and burst.
 The bursting action causes surface agitation, which aids in oxygen exchange at the surface.

More info:

 Clean the sponge every know and then by taking the sponge off of the bottle, squeeze it a few times, and reattach.  
 When drilling the holes, a 15/64th drill bit was used.
 The holes for the tubing should have a smaller diameter than the tubing, to ensure a tight seal