In its simplest form, there is a tray above a reservoir of nutrient solution.

So there's plenty of water - which is expensive to buy - to use for the nutrient solution, a simple 20-10-20 chemical fertilizer.

The containers should exclude light to prevent algae growth in the nutrient solution.

The plants are than fed through a circulating nutrient solution.

Within the growing period, the nutrient solution may require replacement.

But the nutrient solution will be the first limiting factor it'll hit.

Thousands of tiny new plantlets quickly spring from this rich nutrient solution.

The nutrient solution does become concentrated by evaporation, and this is watched.

It was scarcely more than a little sealed plastic balloon, filled with some sort of nutrient solution, my people tell me.

The experimental one had been made in four sections so he could try different pumping systems and nutrient solutions.