Step 2: Plants
In this case I planted some Lettuce along the top (Close together but will thin out latter) and some watermelon seeds along the bottom.
Plants will grow quickly in aquaponic systems.
The plants clean the water for the fish and the fish dirty the water for the plants. What a great cycle :-) The chemistry of it can be found on almost all Aquaponics web sites so type the word into google ( http://www.google.com.au/search?hl=en&q=aquaponics&btnG=Google+Search&meta= ) and learn more. This would be a fun Classroom experiment and an example of natural cycles.