DIY hydroponics: NFT, DWC and soil-less drip

What hydroponics is and what it solves

Growing without soil means water and nutrients reach the root directly. That removes the substrate as a variable: there’s no compaction, no salts building up in the soil and no heavy pots. In return, the system never rests: if the solution sits still or without oxygen, the root rots within hours.

That’s why hydroponics isn’t “watering less”: it’s watering better, but with more responsibility.

• What you need to know: nutrient concentration, pH and oxygenation.
• What you don’t need: substrate or large pots.

The three systems worth setting up at home

NFT (nutrient film technique): the water runs along a slightly tilted channel for a few centimetres and the roots drink from that film. It’s the easiest system to build and also the most sensitive to a stoppage: if the pump fails, the roots dry out within hours.

DWC (deep water culture): the roots hang in a jar with 10-20 litres of solution and an air pump. Because it’s a large volume, it tolerates pump failures better and gives more room for error.

Drip over perlite, coco coir or rockwool: the inert substrate provides no nutrients, only support. It’s the option for larger plants.

The nutrient solution: the heart of the system

This is where the real difference lies between a crop that works and one that goes wrong: plain irrigation water doesn’t feed. You need a complete nutrient solution, with macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium) and micronutrients.

• Always buy a hydroponic base solution, not a garden fertiliser. The difference in concentration and micronutrients is important.
• Two base solutions, one for the growth stage and one with more phosphorus and potassium for fruiting, following what the manufacturer specifies.
• Don’t improvise with kitchen salts: the ratio is easy to get wrong and the consequences show up in the leaves.

FAO-29 explains what the water you use to prepare the solution does to the crop: if it’s saline or carries a lot of sodium, chloride or bicarbonate, the plant pays for it at the leaf tips and in its growth. You adjust the nutrient mix with the datasheet of your substrate and the recommendations from MSU Extension.

pH and EC: the two numbers that matter

pH measures the acidity of the solution. In hydroponics you normally work between 5.5 and 6.5: below that, some nutrients stop being available; above that, iron gets blocked and new leaves yellow even when there’s iron in the water.

EC measures the salt concentration: it indicates how much food is dissolved. It’s expressed in mS/cm and rises as the plant consumes water and nutrients.

Practical rules:

1. Measure the pH at least once a week; in summer, twice.
2. Adjust the pH little by little, with the water at room temperature.
3. Measure the EC before adding nutrients: if the plant is at EC 1.6, don’t fertilise, just top up with water.
4. Change the solution every 4-6 weeks, even if the numbers look good: salts accumulate and micronutrients degrade.

If you can spend 60 euros on an EC and pH meter, it’s the best investment in the system. Without measuring there’s no control, and without control hydroponics becomes watering blind.

Oxygenation: what separates a healthy root from a rotten one

Roots need oxygen. In a well-designed NFT the solution film carries enough oxygen; in DWC and in any system where the water is still, you have to add it.

• Air pump and diffuser in each DWC jar. It’s cheap and it’s the most important thing.
• Never leave the roots in the air: the solution level must cover the roots, but the top part of the root stays outside.
• Keep the water temperature below 22 °C; below that, dissolved oxygen starts to run short. In summer, a fridge with cold water helps.

If you see brown, slimy roots with a bad smell, it isn’t a lack of fertiliser: it’s a lack of oxygen or a temperature that’s too high.

Light: the other limiting factor

Hydroponics multiplies growth, and that means the plant needs more light than in soil, because it’s producing more. Without enough light, any good solution produces stretched, weak plants.

• Indoors: a quality grow light is expensive; an LED horticultural tube is the reasonable minimum.
• Outdoors: balcony, terrace or a bright window. In winter, window sun isn’t enough and you’ll need artificial light.

For the rest of gardening, the same logic as the DIY weather station applies: temperature, humidity and irradiance determine water use.

Building a simple DWC, step by step

1. Opaque container of 15-20 litres with a lid and holes for the mesh pots.
2. Nutrient solution at 50 % of the label concentration to begin with, adjusting as the plant grows.
3. pH adjusted between 5.5 and 6.5.
4. Air pump with diffuser at the bottom of the container. If you connect it to the mains, apply the electrical safety precautions in the garden: the air pump goes in the water and must never share a circuit with the irrigation pump.
5. Mesh pots with coco coir or perlite to hold the seedling.
6. Temperature sensor if the container goes outdoors.
7. Irrigation: in DWC there is no irrigation; the air pump is what keeps the water moving. The automatic irrigation system only helps if you also handle topping up the solution.

When hydroponics isn’t worth it

• If you’re after a big harvest like a garden vegetable plot, hydroponics is more work, not less.
• If you’re not going to measure pH and EC, going back to substrate is preferable: with soil, the margin for error is huge.
• If the space is a narrow window without good light, a seed tray with conventional substrate works better.

Sources and next step

FAO-29 is the reference for water quality in crops (salinity, sodium, chlorides and bicarbonate), and the substrate guide explains when it’s worth going back to the classic method.

External sources

• FAO: Water quality for agriculture (Ayers and Westcot, FAO-29) — water quality limits for irrigation and their effect on the crop.
• MSU Extension: hydroponics — home systems, solution management and growing conditions.