Hydroponics Blog
Root Rot in Hydroponics: Symptoms, Causes, and Emergency Treatment
Quick Answer
Root rot in hydroponics is caused by Pythium species thriving in warm, low-oxygen water. Roots turn brown, slimy, and smell foul. Act within 24 hours. Lower reservoir temperature, increase aeration, and treat with hydrogen peroxide or beneficial bacteria (Bacillus subtilis).
How to Identify Root Rot
| Healthy Roots | Root Rot |
|---|---|
| White or cream coloured | Brown, grey, or black |
| Firm, fibrous texture | Slimy, mushy texture |
| No smell or fresh water smell | Strong foul or sewage smell |
| Dense, spreading root mass | Sparse, falling-apart roots |
Primary Causes
- High reservoir temperature. Above 22–24°C dramatically reduces dissolved oxygen and creates ideal conditions for Pythium. In UAE summers this is the number one cause.
- Insufficient aeration. Low dissolved oxygen in DWC or NFT with blocked channels.
- Contaminated tools or transplants. Pythium spreads through shared equipment.
- Stagnant water. Any water not circulating for more than a few hours in warm conditions.
- Overcrowded reservoir. Too many roots, not enough oxygen exchange.
Emergency Treatment (24–48 Hours)
- Lower reservoir temperature immediately. Target below 20°C. Add frozen water bottles if no chiller available.
- Increase aeration. Add air stones or increase pump size.
- Trim affected roots. Remove brown, dead root sections with sterilised scissors.
- Treat with hydrogen peroxide. 3ml of 3% H₂O₂ per litre of reservoir water. This kills Pythium and oxygenates the water. Reapply after 24 hours if needed. Note: H₂O₂ also kills beneficial bacteria — use it as emergency treatment, not routine maintenance.
- Do a full reservoir flush after treatment. Replace with fresh nutrient solution at correct EC and pH.
Long-Term Prevention
- Keep reservoir below 22°C at all times. Use a chiller in UAE summers.
- Block all light from reaching the reservoir — algae growth worsens oxygen depletion.
- Use beneficial bacteria products (Bacillus subtilis, Trichoderma) as preventative inoculants.
- Clean and sterilise the entire system between grows.
- Never share tools between systems without sterilising.
UAE and Desert Climate Note
In the UAE summer (June–September), ambient temperatures above 40°C can push reservoir water above 30°C even in shaded indoor spaces. A reservoir chiller is not optional for year-round growing in this climate — it is essential infrastructure. Without it, root rot will recur regardless of treatment.