I just put holes around the sides of the top half. I want the water to flow in through the scrubbies then down through the activated charcoal and gravel, then into the bottom of the tube and up and out.
As far as the sock, I cut a small hole into the toe of the sock. I pulled it down from the top with the tube going through the hole in the toe. I pulled it all the way down. Half of the sock was hanging below the bottom, so I pulled it up over the sides and doubled the sock. Like folding your socks over and down at the top when you wear them.
