NFT hydroponic kit : 36 plant sites & pump included

Water from a fish tank carries suspended solids, which the nutrient film tolerates poorly. The particles settle at the bottom of the tube, thicken the film, then block the joints between two levels. If you feed this tower from a pond, mechanical filtration upstream is a condition of it working properly. The rest of the installation does not change: same pump, same slope, same baskets. What you gain in return is water that already carries its nitrates, produced by the nitrogen cycle, so the nutrition needs topping up rather than building from scratch, with particular attention to the iron and potassium that pond water supplies poorly. The pH range also changes, as a stocked pond sits more comfortably between 6.4 and 7.5 to look after the fish and the bacteria, at the cost of slightly lower availability of certain elements to the plants.

Between two cycles, the tubes are taken apart and rinsed with clean water, with the lids open. What you are looking for is the slimy biofilm that forms at the bottom of the channel and traps the particles of the next cycle. Used germination sponges are thrown away, while the baskets are rinsed and reused. Allow a good hour for the 4 tubes, and take the opportunity to empty the tank and scrub its walls, since the deposit starts there. The pump strainer is rinsed at the same time, as a partially clogged filter reduces the flow long before the stream looks abnormal.

Without a grow medium to buffer it, the solution shifts quickly and settles at 5.8 to 6.2, the range in which nutrients remain available. Take a reading once a week on an established crop, every 2 days in the early stages, and always from the tank rather than from a test tube, since the sample there is representative of the whole circuit. The solution should be replaced completely every 2 to 3 weeks, with evaporation topped up in the meantime using clean water. A conductivity that rises while the level drops means the plants are taking up water faster than nutrient salts, and a top-up of clean water corrects this better than adding fertiliser.

The tower takes up less than half a square metre of floor space and mainly needs height, as the tray slides in under the structure. The slope of the tubes is set during assembly and stays slight, about 1 cm per metre being enough to keep the film of water moving without it pooling at the bottom of the channel. Check the side-to-side levelling with the same care, since a tube tilted to one side leaves the opposite edge dry and so a few positions on each row. Finally, allow access on one side to open the tray, measure and top up without moving the whole unit, and a reliable socket nearby for the pump. The assembly itself is done dry, then a first fill with clean water, with the pump running for an hour, checks the watertightness of the joints and the evenness of the water film across the 4 levels before a single plant goes into a basket.