Root Rot on hydroponic lettuce
What's Happening
Root rot in hydroponic systems develops when dissolved oxygen levels fall below 4-5 mg/L, creating anaerobic conditions that favor pathogenic bacteria (Pythium, Phytophthora) and fungi. Unlike soil systems, hydroponic roots are constantly submerged or in high-humidity environments, making oxygen deprivation the primary failure mode. Warm water temperatures above 24°C further reduce oxygen solubility, accelerating anaerobic bacterial proliferation.
How to Fix It
- 1
Immediately increase aeration: add air stones and run air pumps 24/7
- 2
Lower water temperature to 18-20°C using chillers or ice bottles
- 3
Apply 3% hydrogen peroxide at 3-5ml/L as shock treatment for 24 hours
- 4
Remove and discard severely affected plants to prevent spread
- 5
Completely replace nutrient solution and sterilize system with 10% bleach solution
- 6
Rinse remaining healthy roots with fresh pH-balanced water before returning to cleaned system
- 7
Add beneficial microbes (Bacillus subtilis) to outcompete pathogens
How to Prevent It
Maintain dissolved oxygen above 6 mg/L using air pumps and air stones; keep water temperature at 18-22°C; change nutrient solution every 7-14 days; use hydrogen peroxide (3% at 1-2ml/L) weekly as preventive; inspect roots weekly for browning or slime; quarantine new plants for 7 days before adding to system.