Here are some recommendations that we have listed on the kit assembly guides page (http://www.windowfarms.org/kits-guides) that would be helpful for DIY folks.
1) Seat your tube. The base of the water tube needs to be about 1/2″ above the floor of the reservoir. You do not want the base of the water tube to be completely touching the bottom of the reservoir… doing so would not allow water to enter the tube!
2) Keep the water high – Keep the water level in your bottom reservoir high. As the water level drops in the bottom bottles, the pressure on the water column reduces. This situation increases the likelihood of air bubbles escaping from the base of the water tube instead of traveling up inside of it!
3) Adjust your pump – A proper air flow rate is critical to provide enough force to carry water up the water tubes. If the air flow rate is too low, the air flow will not be strong enough to overcome the weight of the water in the tube. In this case, and no water will travel up the tube and instead the bubbles will escape from the bottom of the water tube. To adjust the output rate of the air bubbles, use the knob on top of your pump. NOTE: There are factors that influence the required power setting of the pump, including the length of the airline tube running between the pump and the bottom bottle. Shorter lines are more efficient and will generally require a lower power setting. Avoid having significantly different lengths of airline running to the same pump.
4) Straighten your water tube – Maintaining a straight, vertical, plumb water tube is critical to efficient water flow up the tube. Use tape and/or the plant tape strips to straighten the tube.
5) Add a Tail of tube – Cut a 3″ length from the airline tube running to the pump. Attach the 3″ piece to the ‘free’ end of the black plastic T-valve at the base of the water tube. This will reduce the diameter of the entrance to the air tube, discouraging air from escaping through the end and bubbling back into the water.