This is the aquaponics system as it looks at the moment:
Below you’ll find an overview of the water flow in the system (you’ll have to click the picture to go to the full size drawing):
The water is pumped into the plant tank and due to gravity the water is sucked into the fish tank. It then flows from left to right in the fish tank since the pump sucks up the water in the right side of the fish tank. The water flows from the front of the plant tank to the back and down the drain. This way the water carries nutrients from the fish to the plants.
It’s important that the plant tank is placed higher than the fish tank in order to let gravity do half of the work. The water pump is placed below the fish tank. For the return path I use PVC pipes and for the pump I use aquarium hoses.