I was so close to building one of these setups for my children, but I ruled it out after I thought about all the variables. I can get all the equipment for nothing. I just can't see where it will be maintenance free. I am by no means an aquaponics expert, but I know a lot about salt and fresh water aquariums. You'll have to feed the fish to produce waster and then you have to do something with the waste. Plants will not take up all the ammonia, nitrates, nitrites...... Excess waste = dead fish.
Someone posted an aquaponics setup on this forum that tempted me, but I can't remember who