I did a little video today about lowering the airspeed through to windowfarm to vary (and sometimes increase!) the rate of airlift. Depending on your tubes the rate can be quite slow and still give you good pumping. Check it out because I think it can help people to understand a bit better and to get things right first time.
Anyway here are some pictures that I took out of the video.
This is a little aquarium valve and bottom pic shows the adjustment knobs
You can either use it to regulate air to 2 t joints or just leave one open to the windowfarm and have the other one just a bit open to let some of the air escape.
Below is a head for connecting a tube under the reservoir. You might need a bit of gauze or window bug screen in the bottom to stop crud getting into the tubes.
And you also can use this thing for aquariums as a bottom reservoir.
And finally I am going to show you a pic of the bubble in the tubing.
If you reduce the airflow into the t-joint and into the tube, sometimes the water flow increases. This is because the type of flow changes from churn flow to plug flow.
Plug flow can be quite slow sometimes. As the plugs of water rise, it changes from many short ones to a few long ones.
Watch the video to get more information.