Constructing aquaponics tanks is serious business. While we're working at Mediamatic Fabriek, we're acquiring loads of knowledge we can later share with people, enabling others to make their own aquaponics tanks.
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