Channel slope
1:30 to 1:40 typical
Film depth
Thin — roots not flooded
Best crops
Lettuce, herbs, greens
Target pH
5.5–6.5
Leafy EC
0.8–1.6 mS/cm
Critical risk
Pump failure dries roots
What NFT is designed to do
Nutrient Film Technique flows a shallow stream of nutrient solution down slightly sloping channels. Plant roots sit in the channel; a thin film wets them continuously while the upper root surfaces remain exposed to air. That balance of moisture and oxygen supports fast growth with less water volume than deep reservoirs.
NFT is widely used for lettuce and herbs in commercial and serious hobby setups because plant density can be high, harvesting is convenient, and solution is recirculated from a shared tank. It is less forgiving than DWC or Kratky: if the pump stops, roots can dry within minutes to hours depending on climate and root mass.
NFT is a poor first system if you have never managed pH and EC. Once those habits are solid, NFT rewards you with efficient production and clean, inspectable root zones.
Channel design, slope, and flow
Channels are typically PVC, vinyl, or purpose-made gutters with lids and net-pot holes. A common slope is about 1:30 to 1:40 (roughly a 1–1.5% grade) so solution moves without pooling deeply or racing past roots. Too flat and stagnant pools form; too steep and coverage becomes uneven.
The film should be thin — often described as a few millimeters wetting the channel floor — not a deep flood. Mature root mats will occupy the channel; design so roots do not completely dam the flow. Oversized root masses on long channels are a classic NFT clog risk.
Flow rate depends on channel length, width, and crop. Start with manufacturer guidance for commercial gutters, or empirical tuning on DIY PVC: enough flow that the entire root zone stays moist, not so much that you create deep anaerobic pools at the outlet.
Reservoir, pump, and redundancy
A covered, light-proof reservoir feeds a pump that lifts solution to the high end of each channel. Returns drain to the tank. Size the reservoir for stable chemistry — small tanks swing EC and temperature faster when plants drink heavily.
Use a reliable pump with a pre-filter or strainer so debris and root fragments do not starve channels. Many growers add a backup pump or alarm because NFT has low drought tolerance. Check valves and secure fittings prevent leaks onto floors and electronics.
Keep airline or surface agitation in the reservoir if needed for mixing and dissolved oxygen in the tank itself, but remember primary root oxygen in NFT comes from the air gap in the channel, not from DWC-style deep bubbling alone.
Nutrients, pH, and EC in recirculating NFT
Recirculating NFT concentrates or depletes ions based on plant uptake and evaporation. Measure EC and pH at least daily in productive systems. Leafy greens often run about 0.8–1.4 mS/cm; adjust for cultivar and growth stage. Hold pH near 5.5–6.5.
Top off with water more often than you dump — plants remove water faster than all minerals equally. When EC climbs, dilute; when EC falls and growth is strong, add nutrient according to your dose calculator and recheck. Full reservoir changes on a weekly-to-biweekly cadence keep organic load and imbalances in check.
Avoid heavy particulate additives that settle in channels. Clean filters and inspect inlets regularly. Precipitates from mixing A and B incorrectly will coat channel floors and reduce film uniformity.
Crops that fit NFT — and crops that fight it
Lettuce, leafy greens, basil, and similar herbs are NFT classics. Compact root systems and short cycles match channel geometry. Some strawberry growers use NFT or NFT-like gutters successfully with careful support and runner management.
Large fruiting plants with aggressive roots — indeterminate tomatoes, big peppers — often clog channels, demand more support, and prefer media beds, Dutch buckets, or DWC/RDWC. If you insist on fruiting crops in NFT, use short channels, aggressive pruning, and frequent root inspection.
Seedlings should have established roots before transplant into channels. Cubes that sit too wet in stagnant pockets invite crown rot — ensure the film contacts roots without drowning the stem base.
Environment and channel hygiene
NFT channels heat and cool with the room. Hot solution in long gutters stresses roots similarly to hot DWC water — target roughly 65–72°F (18–22°C) in the reservoir and avoid placing channels in direct sun. Cover channels to block light and stop algae.
Between crop cycles, flush and scrub channels to remove biofilm and root debris. Biofilm reduces flow and harbors pathogens. In continuous production, stagger cleaning by channel so you never shut the entire farm at once.
Provide canopy airflow and appropriate PPFD for greens (often 200–400 µmol/m²/s). High-density NFT can create humidity pockets — manage VPD to reduce tip burn and foliar disease while avoiding excessive transpiration that empties the tank too fast.
Operating checklist for reliable NFT
Before planting: verify slope, even flow to every site, no leaks, covered reservoir, calibrated meters, and a pump strainer in place. Map which channel is fed by which manifold outlet.
During production: daily pump confirmation, EC/pH logging, water-level checks, and quick walks for dry sites or pooling. Weekly deeper inspection of filters, returns, and root color at a few sample sites.
On failure: restore flow first. Wilting NFT plants often recover if re-wetted quickly and not heat-stressed. After outages, check for damming root mats and flush channels if debris shifted.
Frequently asked questions
How is NFT different from DWC?
DWC submerges roots in a deep oxygenated reservoir. NFT wets roots with a thin flowing film in a sloping channel while much of the root surface stays in air. NFT uses less water volume per plant but fails faster if the pump stops.
What slope should NFT channels have?
A common starting range is about 1:30 to 1:40 slope. Adjust so solution moves as a thin film without deep pooling or dry stretches. Manufacturer gutters often specify exact grades.
Why are plants wilting at the end of my NFT channel?
Flow may be insufficient, roots may be damming the channel, or the slope may be wrong. Check pump output, clear blockages, and confirm the film reaches the outlet plants.
Is NFT good for beginners?
It is intermediate. Learn pH, EC, and root health on DWC or Kratky first. NFT rewards experience but punishes pump failures and clogged channels more harshly.
Related tools & plant guides
- Reservoir Volume Calculator — Calculate the volume of your reservoir in litres or gallons based on container dimensions.
- Nutrient Mixing Calculator — Calculate exact nutrient amounts for your reservoir based on volume and concentration ratios.
- EC ↔ PPM Converter — Convert between Electrical Conductivity (EC) and PPM across 500, 640, and 700 TDS scales.
- Hydroponic Lettuce guide — pH 5.5–6.5 (aim 5.8–6.2), EC 0.8–1.2 mS/cm
- Hydroponic Basil guide — pH 5.5–6.5, EC 1.0–1.6 mS/cm
- Hydroponic Spinach guide — pH 5.5–6.6, EC 1.8–2.3 mS/cm
- Hydroponic Strawberries guide — pH 5.5–6.2, EC 1.0–1.8 mS/cm
Keep measuring
Pair this guide with free hydroponic calculators, crop targets in plant guides, and meter picks in product reviews.