A interesting part of construction is the siphon. This is a system used to create tides in water. The siphon consists of two tubes, one inside of the other. The outer tube sealed on the top and the inner-tube with an exit hole at the bottom for the water to escape the grow-bed. Once the water level reaches the top of the inner-cylinder and starts flowing in a vacuum is created shortly after by this same water. This vacuum makes all the water flowing out of the grow-bed until this vacuum is broken. This breaking of the vacuum happens when the water level comes below the bottom of the outer-cylinder.
Here a simple diagram on how we would like to warm our water by using the warmth of the LEDs. In this link you can see how someone did a DIY version of this for his aquarium.
This is a drawing of the water flow in an aquaponics system
About the growlights