[Geofrog]

I created the image in powerpoint so it's not the best.

Here's the step by step:
1. Cut the bottoms off of a 1l and a 500ml water bottles.
2. Cut some slits near the top of the 1l bottle, long enough to be partially submersed when done.
3. Use PVC adhesive on the top of the 500ml bottle and inside the neck of the 1l bottle.
4. Insert the smaller bottle and let the adhesive dry (30 min.)
5. Once dry, poke a hole just below the level of the inner bottle big enough for your airline. Feed some airline through and attach airstone so that the airstone will fit into the inner bottle from the bottom.
6. Cut a hole big enough to fit the bottle neck in the base of a sour cream container or similar. Also punch a small hole on the side of the collection cup to allow water to drain.
7. Using a cold temp "hot" glue gun, glue the collection cup to the skimmer.
8. Glue suction cups to side of skimmer. I used the heater suction cups (replacement cost ~$1.50).

Attack to tank and trun on the air, within a few minutes you will start to get skimmate in the collection cup. To adjust the flow, just move the skimmer up and down. More water enter the slits = more skimmate.