In another thread I mentioned that I would soon start a new trial in hydroponics and – for everyone’s information and comment – this is what I have in mind doing: Nutrient film technique (NFT) is a hydroponic technique developed in the mid 1960s, wherein a very shallow stream of water containing all the dissolved nutrients required for plant growth is re-circulated past the bare roots of plants in a watertight gully, also known as channels. In an ideal system, the depth of the recirculating stream should be very shallow, little more than a film of water, hence the name 'nutrient film'. This ensures that the thick root mat, which develops in the bottom of the channel, has an upper surface, which, although moist, is in the air. A properly designed NFT system is based on using the right channel slopes of 1:30 to 1:40, the right flow rate of 1 liter per minute, and the right channel length which should be less than 10 – 15m. The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen and nutrients and is – consequently - the most productive form of hydroponics. Ex: Wikipedia This is - almost exactly - what I have in mind building.In an effort to supplement plant nutrients, I originally had in mind to install a filter in the bottom reservoir and stock it with fish to produce food-waste that can be converted to plant-growing nutrients. However, that would force me to do regular measurements of the nutrient concentrations in order to maintain the correct levels for the plants under cultivation but that will – obviously – make the fish superfluous. So I eventually decided to leave out the fish but keep the filter.