This is another mini-project made of recycled materials. It's the cheapest mini-project to date, under (!), but ended as a fail.\n\nWe had a couple of empty plastic bottles lying around and I knew we could make something with it and I decided to see if we could make a mini protein skimmer. All it is 2 empty water bottles joined by a 90 deg elbow. The vertical water bottle has a small hole drilled on top for water intake and a bio-ball and some cut up straws at the bottom.\n\n[URL=http://img185.imagevenue.com/img.php?image=788899087_foam1_122_47lo.jpg][IMG]http://img185.imagevenue.com/loc47/th_788899087_foam1_122_47lo.jpg[/IMG][/URL]\n\n[URL=http://img45.imagevenue.com/img.php?image=888991669_foam2_122_206lo.jpg][IMG]http://img45.imagevenue.com/loc206/th_888991669_foam2_122_206lo.jpg[/IMG][/URL]\n\n[URL=http://img258.imagevenue.com/img.php?image=788899281_foam3_122_81lo.jpg][IMG]http://img258.imagevenue.com/loc81/th_788899281_foam3_122_81lo.jpg[/IMG][/URL]\n\n\nThe horizontal bottle has a mini-bulkhead fitting and 90 elbow poking out in the middle and another hole drilled at the end for water outlet. The water outlet has a small curved 5/16 piece of tubing in it. The water level in the horizontal bottle can be adjusted by moving the the curved tubing in and out.\n\nThe theory is that water coming in from the top of the vertical water bottle goes down the cut up straws creating a lot of water/air interface and bubbles which then fall into the horizontal tube with the water and then exit through the 90 degree elbow. The DOC (dissolved organic compounds) or gunk will be attracted to the bubbles and exit with them.\n\nThe main problem with this project, like the last one is that you can only miniaturize down to a certain point. At some point, there isn't enough water flow, pressure or distance to create similar conditions that a bigger one can. In this case, there wasn't enough water flow coming from the mini-water pump or height to create enough bubbles.\n\nI'm thinking about modifying this to either\n1) add more cut up straws to create more water/air contact\n2) remove straws and bioball because I think at this size, the action of the stream of water falling on water will create bubbles itself\n3) upsize to 2 liter bottles and a bigger pump to make it work.\n\nAs a functioning protein skimmer it was a failure but as a father/son project it was a success!