Aquaponics- what does it mean?

The word is a combination of Aquaculture and Hydroponics.
Basically it is the setting up of a self contained system which uses fish to produce nutrients for bacteria which convert ammonia compounds into nitrites and then nitrates which are taken up by plants which in turn purifies the water and make concentrations of fish which would not otherwise be possible.
If all goes according to plan I should be able to raise at least 100kg of fish per year in 4000 litres of water. That is 2.5kg of fish per 100 litres of water which is actually a fairly conservative stocking rate.
Needless to say the system needs to be carefully balanced and that is the real trick. If any part of the scheme fails the whole thing will fall over and neither fish nor plants will thrive and/or survive.
Versions of aquaponics have been in use for thousands of years so it is nothing new.