NFT — Nutrient Film Technique — is the system you picture when you imagine commercial hydroponics: tidy rows of lettuce sitting in long white channels, a thin stream of nutrient solution sliding past their roots. It looks high-tech, but the underlying idea is almost embarrassingly simple. A shallow film of water, just a millimeter or two deep, runs continuously down a gently sloped channel. Plant roots sit in that channel, the top half exposed to air and the bottom half bathed in the moving film. They get water, dissolved nutrients, and oxygen all at once, which is exactly the combination that drives fast, clean growth. For a small-space grower — a balcony, a spare shelf, a garage wall — NFT packs a lot of plants into a small footprint and uses very little water. This guide covers every component, how to build and slope a system, the pump and reservoir math, your pH and nutrient targets, and which crops actually thrive in NFT versus the ones that fight it.
Key Takeaways
- How it works: A thin film of nutrient solution flows continuously down sloped channels past bare roots, delivering water, food, and oxygen at once.
- Slope: Aim for a 1:30 to 1:40 fall — roughly a 1-inch drop over every 3 feet of channel.
- Flow rate: Target about 1 liter per minute (0.25 GPM) per channel; a small 200–400 GPH pump runs several channels.
- Nutrients: Leafy greens want EC 1.2–1.8 and pH 5.5–6.2; check and top up the reservoir every few days.
- Best crops: Lettuce, herbs, bok choy, spinach, and strawberries. Avoid heavy fruiting or tall, top-heavy plants.
- Weak point: NFT has no buffer — a pump failure dries the roots within hours, so reliable flow is non-negotiable.
How NFT actually works
In a Nutrient Film Technique system, nutrient solution is pumped from a reservoir up to the high end of a channel, where it spills in and begins flowing downhill by gravity. Because the channel is only slightly tilted, the water doesn’t rush — it forms a shallow, slow-moving film across the channel floor. Plant roots, supported at the top by net pots or a notch in the channel lid, trail down into that film. The genius of the system is that roots are never submerged. The tips in the film drink and feed; the mass above the film sits in humid air and breathes. That constant access to oxygen is why NFT plants rarely suffer the root suffocation that plagues poorly aerated deep-water systems.
At the low end of the channel, the solution drains out and returns to the reservoir, where the pump sends it around again. It’s a closed loop, which is why NFT uses a fraction of the water a soil garden does — almost nothing is lost except what the plants actually transpire. The trade-off is that the system runs continuously and holds very little water in the channels themselves. There is no reserve. If the pump stops, the film drains away in minutes and those exposed roots, with no soil or reservoir of moisture around them, begin to dry almost immediately. Everything about building a good NFT setup comes back to keeping that film flowing reliably.
The components you need
Channels (the grow gullies)
The channel is the heart of the system. Purpose-made NFT channels are flat-bottomed extruded plastic — flat-bottomed matters, because round PVC pipe concentrates the film into a narrow trickle down the center and leaves outer roots dry. If you do use round pipe to start cheaply, 3-inch or 4-inch PVC works for small crops, but a flat 4-inch by 2-inch gully gives a wider, more even film. Drill holes or fit a lid with planting sites spaced for your crop: roughly 6–7 inches apart for lettuce and most greens, 8–10 inches for larger heads. Keep channel runs under about 30–40 feet; beyond that the plants near the far end get a nutrient-depleted, slightly warmer film.
Reservoir
A food-grade opaque tank holds the nutrient solution. Opaque is important — light in the reservoir grows algae, which clogs lines and competes for nutrients. Size it generously: a bigger reservoir buffers swings in pH, EC, and temperature, so the whole system is more forgiving. For a small home setup of two to four channels, 10–20 gallons is plenty. The rule of thumb is at least half a gallon of reservoir per plant site for greens, more for thirsty crops.
Pump and plumbing
A submersible pump pushes solution up to the channels through flexible tubing and a manifold that splits flow to each gully. For a handful of channels a 200–400 GPH pump with adjustable flow is ideal. You want enough head height (the vertical lift to the top of the channels) in the pump’s rating to still deliver flow once it’s raised — a pump rated 300 GPH at zero lift might only move 150 GPH at 4 feet, so check the pump’s flow-versus-height curve. Return lines simply drop the drained solution back into the reservoir by gravity.
Net pots and media
Seedlings are started in small plugs — rockwool cubes, Oasis foam, or coco coir — and dropped into 2-inch net pots that seat into the channel holes. A little media at the crown holds the seedling upright until its roots reach the film; after that the roots do the work. Round out the kit with an air pump and air stone in the reservoir (extra dissolved oxygen never hurts), a digital EC/TDS meter, a pH meter, and pH-up and pH-down solutions.
Setting up: slope, flow, and assembly
Start by building a stable, slightly tilted frame to hold the channels. The single most important number in NFT is the slope. Aim for a gradient between 1:30 and 1:40 — that is a drop of about 1 inch for every 3 feet of channel length. Too flat and the film pools, stagnates, and drowns roots; too steep and the water races through too fast to feed evenly and roots near the top dry out. A long spirit level and a tape measure are all you need to set it. Make sure the whole channel falls in one direction with no dips, because a single low spot creates a puddle that breeds rot.
Next, dial in the flow rate. For each channel you want roughly 1 liter per minute, which is about a quarter gallon per minute — enough to keep a continuous film without flooding. Run the pump, watch the film, and adjust the manifold valves until each channel shows a thin, even, fast-moving sheet of water across its full width, not a single central stream. Position the reservoir directly below the low ends of the channels so the return lines drop straight in. Run the system with plain water for a day before planting to confirm there are no leaks, no dry channels, and no overflow, and that the film reaches every planting site.
Most home growers run the pump continuously, 24 hours a day, because the roots depend on the film never stopping. Some growers cycle the pump on a timer (15 minutes on, 15 off) to save energy, but this is riskier for beginners — any error in timing leaves roots dry. Until you trust your setup, leave it running. If you are building this on a balcony or in a small indoor footprint, our urban gardening hub has more space-efficient growing ideas to pair with it.
Nutrients, EC, and pH
NFT plants get every bit of their food from the water, so the nutrient solution has to be complete and balanced. Use a two-part or three-part hydroponic nutrient designed for the technique, mixed to the strength your crop wants. Strength is measured as EC (electrical conductivity) or its cousin TDS/PPM. Leafy greens and herbs are light feeders — target an EC of about 1.2 to 1.8 (roughly 600–900 PPM on the 500 scale). Fruiting crops like strawberries want it stronger, around EC 1.8 to 2.4. Mix nutrients into water first, then adjust pH.
pH controls whether those dissolved nutrients are actually available to the roots. For hydroponics the sweet spot is 5.5 to 6.2; drift much outside that band and elements lock out even though they’re present in the water, showing up as yellowing or stunting that looks like a deficiency but is really a pH problem. Check pH and EC every two to three days with your meters. As plants drink, the water level drops and the solution concentrates, so top up with plain pH-adjusted water to keep the level steady, and do a full reservoir change every one to two weeks to reset the nutrient balance and flush salts. Keep solution temperature in the 65–72°F range — warm water holds less oxygen and invites root rot pathogens like pythium.
The best crops for NFT (and the ones to skip)
NFT was designed around fast, lightweight, shallow-rooted crops, and that’s where it shines. Lettuce of every type is the classic — loose-leaf, romaine, butterhead — going from seedling to harvest in four to six weeks. Leafy greens and herbs are the whole sweet spot: spinach, bok choy, Swiss chard, kale, arugula, basil, cilantro, mint, parsley, and chives all do beautifully. These plants have modest root systems and stay light enough that the channel supports them without the roots forming a dense mat that dams the film.
Strawberries are the standout fruiting crop for NFT — compact, productive, and well-suited to channel growing, which is why you see them in so many commercial vertical NFT farms. Where NFT struggles is with big, top-heavy, or heavy-feeding plants. Tomatoes, peppers, cucumbers, and squash grow large root masses that quickly clog a channel and block the film, and their weight needs more support than a gully provides; they’re far happier in Dutch buckets or deep-water systems. Root crops like carrots and potatoes obviously don’t fit a system with no growing medium. Start with lettuce and herbs, get your slope, flow, and pH dialed in, and branch out from there. For another beginner-friendly small-space build, see our keyhole garden guide.
Common problems and fixes
Dry roots near the channel top
The film isn’t reaching the high end evenly. Increase flow to that channel, check for clogs in the manifold, and confirm the slope has no early dip.
Yellowing or stunted plants
Usually pH drift locking out nutrients, or a depleted reservoir. Test pH and EC, correct them, and change the solution if it’s been more than a week.
Slimy brown roots
Root rot from warm, low-oxygen solution. Cool the reservoir, add an air stone, and consider a beneficial-microbe additive; remove affected plants.
Algae in channels or reservoir
Light is reaching the solution. Use opaque channels and tank, cover any clear surfaces, and keep planting holes filled.
Frequently Asked Questions
What slope should an NFT channel have?
Aim for a gradient of 1:30 to 1:40 — about a 1-inch drop per 3 feet of channel. Too flat and the film pools and stagnates; too steep and roots near the top dry out. The whole channel should fall in one direction with no dips.
Should I run the pump all the time?
For beginners, yes — run it continuously. NFT holds almost no water in the channels, so if the pump stops, the film drains and exposed roots dry within hours. Timed cycling saves energy but is risky until your system is proven reliable.
What pH and EC should the solution be?
Keep pH between 5.5 and 6.2. For leafy greens and herbs target an EC of 1.2–1.8; fruiting crops like strawberries want 1.8–2.4. Check both every two to three days and change the reservoir every one to two weeks.
What grows best in an NFT system?
Fast, lightweight crops: lettuce, basil, spinach, bok choy, kale, arugula, and other leafy greens and herbs, plus strawberries. Avoid heavy fruiting or tall plants like tomatoes, peppers, and cucumbers, whose large roots clog channels.
How big a pump and reservoir do I need?
For two to four home channels, a 200–400 GPH adjustable pump and a 10–20 gallon opaque reservoir are ample. Aim for about 1 liter per minute of flow per channel, and check the pump delivers that once raised to channel height.
NFT rewards attention to a few key numbers — slope, flow, pH, and EC — and punishes neglect of the one thing it can’t survive: a stopped pump. Get the film flowing evenly, keep the solution balanced, start with lettuce and herbs, and you’ll be cutting fresh greens within weeks from a system that fits on a single shelf and sips water. Master the basics on leafy crops first, and the rest of the hydroponic world opens up from there.