I use pvc pipe & a section of pond filter to make sponge filters. Take a 8 or 9" piece of 1/2" pvc, and a 4" cube of foam. Drill a bunch of holes crosswise through the pvc at 1 end, making sure they don't extend past the size of the sponge you use. Put a cap on this end. On the other end, drill a hole close to the end, around 1/2" from the end, that's big enough to pass an air line through.
l. l Air line hole
l l
l l
l l
l...l cross
l...l holes
l_ l cap
Poke a hole through the sponge, and shove the drilled & capped pvc through. Make sure the sponge covers all the holes. Pass the air line through the top hole from the outside & push it down to the cap. Put a but of gravel down the pvc to weigh it down, otherwise it will float. Hook it up to the air pump, squeeze some air bubbles out of the sponge while it's in the tank, that's it.
Leaving the sponge above the cap makes it so it doesn't sit flat on the bottom, trapping fry. Kind of a tripod thing. The air line hole keeps the air line from working it's way out, and you can move it around using the air line without worrying about pulling it out.
HTH!
Tolak
