Hydroponics Truths: Debunking Myths That Kill Crops

Hydroponics is rife with misinformation. Here are the field-tested rules that separate harvests from failures.

Water Temperature: 21°C (70°F) Exactly

• Feels cool, not warm. Holds max oxygen.
• Above 21°C = less O₂ = root stress.

NFT Pumps Run 24/7

• Once roots exit starter cubes, never off >15 min—even lights-out.
• Off periods = evaporation cooling = root cell damage (brown roots).
• Constant flow stabilizes root-zone temp.

CO₂ in Nutrient Solution? No.

• Leaves use CO₂; roots need O₂.
• Adding carbon to solution does nothing (unless in specific additive complexes).

EC Meters: For Tuning, Not Targets

• Source water EC varies wildly—no universal "ideal number."
• Use meter to maintain your determined optimum daily.

Feed Strength: Genetics + Environment

• Not all plants eat alike—even same variety.
• More light = more food.
• General: ¼–½ strength (young), ½–¾ (mature). Full strength ≈ 1200 ppm / EC 1.7.
• Tomatoes want more; lettuce wants less. Test your variety.

Leaf Fade + Rust Spots = Environment, Not Food

• Unless severely under/overfeeding, look at: light too close, nutrient too warm, low air exchange, cold nights, wind burn, dry air.

Stretching: No Single Cause

• Low light, high heat, genetics—all possible. Don't accept one-size diagnoses.

Input Air: Use Indoor Air

• Better temp, higher CO₂. Outdoor air brings temp/humidity/bug swings.
• Exhaust to outside or another room.

Air-Cooled Reflectors: Blow, Don't Suck

• Fan must push air through shade. Pulling cools poorly.

pH Drift in Recirculating Systems

• Rises daily (especially rockwool + hard water).
• Don't hammer it down daily—excess phosphoric acid = nutrient lockout.
• Let it drift 1–2 days. Disturb roots as little as possible.

Night Temp Stability = Yield

• Hold 21°C lights-off. Cold nights slash production.

Control the variables. Trust the data. Ignore the noise.