I got some black and white "Indo-Pacific" aragonite live sand. This is better quality and a much finer grain than the coarse black sand I already had on hand. I was planning on mixing them, but then I thought this might be a good starting point for a jaubert type filter (they have different layers of substrate, right?).
Yes, the Jaubert method uses different layers, but not like you indicate. Sand grain size is important; around 2-4mm is recommended. Seems various sizes are okay as long as they are within this size range.
Does anyone have some simple plans for building your own plenum? I especially am interested in instructions for converting existing undergravel filters into plenums. Can it be as easy as kitchen shears and epoxy?
PVC pipe (around 3/4" inner diameter) and eggcrate (commonly used in light fixtures and available ay many hardware stores) is easy to use.
Very basic instructions:
Assemble PVC sections into a box or frame that covers the perimeter of the bottom of your tank. Depending on size, you may need additional row(s) of pipe down the middle for support.
Note: You may want to leave a 1/4 to 1/3" gap around the sides so that this thing is not visible from the outside and to make sure the empty plenum area receives no light.
Take fiberglass window screen and wrap the PVC and eggcrate much like a holiday present. Use fishing line to hold the overlapping screen together.
Place this construct in the tank and add enough sand so that it is 2" deep (or total of 3" if you include the height of the eggcrate & PVC)
Place a single layer of fiber glass window screen on the sand. Make sure the entire top of the sand layer is covered. This helps ensure that the plenum is not distrubed.
Add another 2" inches of sand on top of the screen. You should now have an approximate sand depth of 5 inches.
What materials can I use for the dividing net and for the insulating wool? Can I get them at a hardware store?
I'm not sure why you mention insulating wool. Normal fiberglass window screen should be fine for the dividing net.
Bob Goeman's "Live Sand Secrets" books is highly recommended.
I used his advice when setting up my 12gal nano tank. It's worked well for me, but for others - their results have varied. Proper construction of the plenum, setup of the tank (leave around 75% of the sand bed uncovered) and maintenance is important.
