Glad the bird bath is back together - not so good about your fingers Rhubarb. Lexy, have you got decen weather ? It is just bucketing here still.
The Aquaponic system is basically a mini ecosystem which combines hydroponics and aquaculture. In hydroponics the water needs dumping regularly to deal with the build up of nutrients. With Aquaculture the water builds up high levels of nitrates that need dealing with.
An Aquaponic system consists of a fish tank with a growbed /growbeds on top or by the side depending on design. The water from the fish tank containing the fish waste is pumped through the grow bed which acts as a filter. Bacteria in the grow bed breaks down the fish waste to nitrites which then get converted to nitrates. The plants in the growbed are able to take up the nitrates and use them for growth. The water is then effectively filtered and returned back down to the fish tank. there are also worms which live in the water in the grow bed and breakdown some of the fish solids and plant roots.
Once the system has cycled as you would when starting up a normal fish tank, maintenance is low. Every so often the water level needs topping up and you need to keep an eye on the pH as it needs to be a certain level for the bacteria to keep working and for the plants to be able to take up the nitrates. I chuck shells into the grow bed to keep the pH steady. There aren't any weeds to worry about and the plants can be planted much closer than in the ground so higher yield from small space. The fish do need a handful of food chucked in daily but that's pretty much all I have done since the New Year when the cycling completed.
There are 6 little Koi in the tank, they will get too big eventually so I'll get a bigger tank or sell them. In the grow bed I've a couple of climbing beans, garlic, leeks, lettuce, red cabbage and oriental greens at the moment. My colleague started with a couple similar to mine but has a big polytunnel. After major success with chilli plants in it last summer which has led to a small but expanding chilli sauce business, he's expanded. He's dug out a pond and is going to have 12 or 14 grow beds which hopefully will give him all the chillis he needs. It's quite big out in Oz I think and that's where the main forum is, with people from all over the world. Quite addictive, it's usually a matter of when you expand the system rather than if !
Sorry, that is very very long.