This is a prefabricated filter sock I tried to copy. I began reusing the plastic piece on the top of the sock.

    I have made MANY of these filter socks and abandoned using the plastic lip around the top and the 'PVC Hanger' (shown below). I find it MUCH more convenient using a sewn on handle. I also quit making the sock with the cardboard stencil, it was a waste of material. Now I just make them rectangular like shown below.
 

You may ask "how can I hang this sock"? Shown below:
Sewn On Handle			4" PVC Hanger

    Filter socks are quite probably the best means to mechanical filtration for an aquarium. Filter socks not only filter out fine debris from your overflow, they also filter out micro bubbles. One can direct the output of their protein skimmer into a filter sock to ensure any stray micro bubbles do not stray throughout the sump or find their way to the display tank.

ADVANTAGES:

• Filter socks are passive, meaning they do not create back pressure with the plumbing system like "canister filters" do. When a sock becomes completely clogged it will simply overflow. Just change them before they become clogged.
• Filter socks are much easier to maintain in comparison to other filtration methods
• Filter socks are cheaper to make than they are to buy.
• Does not require an additional pump
• Uses no electricity
• Reusable many times over

Materials:

• 72" White Craft Felt, 100% Polyester $4.99/yd

CLEANING - MAINTENANCE:

• Turn inside out
• Spray off any debris and junk that can easily be removed
• Leave 'inside out' and throw it in the washer machine 'all by itself'. DO NOT use detergent or bleach

PRICE:

• The price per sock depends on the dimensions of the filter sock made. I make my filter socks approx 9" x 16-1/2"
• 2 yards of felt
• 2 lineal yards of cotton handle material
• Makes 18 filter socks

TOTAL COST = approx $10.00

PRICE EACH = 56¢