Hydroponics

What is hydroponics?

Hydroponics is growing plants without soil. The roots sit in water, in a flowing nutrient solution, or in an inert medium such as clay pebbles, rockwool or coco that holds the plant up but feeds it nothing. Everything the plant eats is dissolved in the water you give it, from a bottle of nutrients measured out to a feed chart.

That is the whole trick, and it explains both the appeal and the catch. Because the roots get water, food and oxygen at the same time, and never have to search for any of them, plants grow noticeably faster than in soil and you decide exactly what they are fed and when. Because there is no soil to buffer your mistakes, the feed strength (EC) and acidity (pH) of the solution have to be right, and checked. A pH and EC meter is the one tool every hydroponic grower owns.

In the UK, "hydroponics" covers a family of systems that move the solution to the roots in different ways, and a family of shops, like ours, that sell everything indoor growing needs whether or not the plants ever touch water. The systems are compared below; the tents, lights and fans that go round them are further down.

The systems compared

Deep water culture (DWC)

The simplest system: a plant in a net pot of clay pebbles sits in the lid of a bucket of nutrient solution, an air pump bubbles oxygen through an air stone underneath, and the roots hang straight down into the water. Growth is very fast and there is almost nothing to go wrong mechanically, but the water must stay cool (about 18 to 22 °C) and aerated, so it suits one to four large plants in a room that does not overheat. We do not stock a boxed DWC kit; growers build one from a bucket with a lid, a Hailea air pump, air stones and airline from pumps and aeration, and a bag of Canna Aqua clay pebbles.

Nutrient film technique (NFT)

A tank with a sloping tray on top. A pump lifts the solution to the top of the tray, it runs back down as a thin film over a spreader mat the roots grow into, and drains into the tank again all day. Plants start in rockwool cubes and sit straight on the tray, so there is no medium to buy or throw away, and it fits a lot of growth into a small footprint. It suits growers who will check the tank every day or two. The GT205i is the starter tank (20 litres, 70 × 39 cm, with pump, tray, Correx top and spreader mat), the GT604 holds 60 litres and up to six plants under one 600 W light, and the GT100 puts a square metre of tray on a 100 litre tank. All in NFT systems.

Flood and drain

Each plant sits in a pot of clay pebbles (or a 60/40 pebble and coco mix) in its own tray, all fed from one central tank. Several times a day the brain pot pumps the solution out to flood every tray; the roots drink, then it all drains back and pulls fresh air down through the pebbles. It scales from six pots to a room on one timer and is the system of choice for growers who want bigger plants than NFT allows and a tank they can walk away from. The IWS Flood & Drain has been the standard modular system for around twenty years (6 to 48 pots, 9.5 litre punched pots or 5.5 litre net pots); the IWS PRO uses bigger fittings for a faster flood, and the Trident is the newer design in 16 and 25 litre pots. All in flood and drain systems.

Dripper systems

A pump in the tank pushes solution through thin pipe to a dripper or a ring at each pot, on a timer, for a minute or two several times a day, and the run-off drains back. It works in coco, rockwool or pebbles, gives every plant the same dose at the same moment, and is the closest thing to hand watering in pots, only automatic, so it suits growers moving up from soil. The Origin System is a tray, four pots (6 or 11 litres) and a 30 litre reservoir sized for a 60 cm tent, with larger versions to 115 cm; the Origin 8 XL runs eight 11 litre pots; the IWS Dripper System Pro stands each pot over a return tray and runs from 4 to 48 pots on a FlexiTank. All in dripper systems.

Autopot

Not strictly hydroponics, but the simplest way to automate watering in soil or coco. A tank feeds each pot by gravity through an AquaValve in the tray under it: the valve fills the tray to 20 mm, closes, and does not open again until the tray is dry, so each plant waters itself and gets a dry period. No pump, timer or electricity, and it copes with a week away. Autopot recommend good soil (Plagron Light Mix or Canna Terra Professional) over a 40 to 50 mm layer of clay pebbles rather than a hydroponic medium. The 4-Pot system with 47 litre tank runs a square metre under a 600 W light and lasts three to five days between fills with big plants; the 1-Pot system keeps a specimen or mother plant for over ten days; the Tray2Grow does the same for seed trays and salads. Systems come in 15 litre, 25 litre XL and FlexiPot fabric versions from one pot to 48.

What you need around the system

• A tent. A grow tent keeps the light in and lets you control the air; 100 × 100 and 120 × 120 cm are the sizes the systems above are made for. See what size grow tent do I need?
• A light. One LED of 300 to 720 W depending on the tent, or a 600 W HPS. Our LED wattage guide has the table.
• Ventilation. An inline fan and carbon filter sized to the tent (how to size them), and a clip fan to move the air inside.
• Nutrients. A hydro or coco base nutrient run to the maker's chart (Canna Aqua, Plant Magic Hydro), pH adjusters, and the meters to check them. If your tap water is hard, an RO filter is worth considering for NFT and DWC.
• Media. Clay pebbles (20 or 45 litre bags) for flood and drain, DWC and Origin pots; rockwool slabs (100 or 130 cm) and cubes for NFT and drippers; Canna Coco Professional Plus for drippers and Autopot mixes. All under growing media.
• Water on the move. Submersible pumps (3500 to 12000 l/h), air pumps and stones, and tanks from a bucket to a 750 litre FlexiTank, with the fittings and pipe to join it all.
• Somewhere to start the plants. Cuttings and seedlings root in a propagator in rockwool or plugs before they go into any of the systems.

Everything above, from a single AquaValve to a 48-pot room, is under hydroponic systems and irrigation. If you would like a system sized to your tent, call the shop on 0117 971 3000 with the tent size and the number of plants.

Hydroponics questions we get asked

What is hydroponics?

Growing plants without soil, with their roots in water, a nutrient solution, or an inert medium such as clay pebbles, coco or rockwool that holds no food of its own. Everything the plant needs is dissolved in the water you give it.

Is hydroponics better than soil?

It is faster and it gives you control: roots get water, food and oxygen at once, so plants grow quicker and you decide exactly what they are fed. Soil is more forgiving of mistakes and needs less checking. Many growers run soil or coco in an Autopot system, which is the best of both.

Which hydroponic system is best for beginners?

A small NFT tank such as the GT205i, or an Autopot system in soil or coco. Both are cheap, quiet and hard to get wrong. Deep water culture is simple too but needs the water temperature and oxygen watched.

Do I need special nutrients for hydroponics?

Yes: a hydro or coco base nutrient made to be the plant's only food, run at the EC and pH the maker's feed chart gives, and pH adjusters and a meter to check it. Soil feeds rely on the soil to do part of the work.

How often should I change the nutrient solution?

Weekly is the usual rule for a recirculating tank, topping up with plain water between changes and checking EC and pH every day or two. Autopot tanks are not recirculated, so they are refilled rather than changed.