Brown, slimy roots (root rot / Pythium)

Roots are brown, slimy and smell like a swamp. Plant wilts even though the reservoir is full.

Commonly affects: All hydroponic crops

What you'll see

Roots brown, mushy or slimy instead of bright white
Foul, swampy smell from the reservoir
Plant wilts during the day even with water available
Sudden yellowing and collapse

Likely causes

Reservoir water too warm (>22 °C) — biggest single cause
Low dissolved oxygen (no airstone or pump too small)
Light leaking into the reservoir, growing algae
Old, stagnant nutrient solution (>3 weeks without change)
Pathogen introduced on dirty equipment or unsterile media

How to fix it (step by step)

1Isolate affected plants where practical and clean empty equipment according to equipment and disinfectant labels
2Seek qualified advice for affected roots; colour alone does not confirm a pathogen or justify pruning
3Obtain crop-specific advice before refilling; do not combine nutrient changes and root treatments without checking compatibility
4Add or upgrade airstone — aim for vigorous bubbling
5Block ALL light from the reservoir (black tape, foil, opaque lid)
6Cool the reservoir to under 21 °C — frozen bottles, chiller, or insulation

Stop it happening again

Keep reservoir below 22 °C at all times
Determine replacement needs from water quality, hygiene, crop and system conditions
Sterilise equipment between crops
Use opaque, sealed reservoirs

Need a second opinion?

Share dated photos, root observations, water readings and your mixing record so our team can assess the problem. Visual symptoms alone do not confirm a diagnosis.

Confirm the cause before treating the crop

Collect observations that distinguish possible causes

Record the first appearance of symptoms, the affected plants and whether old or new tissue is involved. Inspect roots, delivery and visible pests. Compare a healthy plant nearby. Record pH, EC, temperature and recent changes. Several causes may act together; the symptom title is a starting point, not a confirmed diagnosis.

Verify calibration and the complete mixing record. Product links explain nutrient roles; they are not instructions to use one bottle alone. Record your correction and assess subsequent growth because damaged leaves and fruit may not recover.

Escalate safely

Rapid wilting, collapse or spreading root symptoms need prompt checks of flow, oxygen and hygiene. Protect unaffected plants where practical and seek qualified diagnosis. Treatments must be registered for their intended crop and use and applied according to label, including harvest intervals.

When asking for help, provide dated root and leaf photos, water readings and mixing records. Do not combine nutrient changes with disinfectants or pesticides without compatibility advice. An online guide cannot confirm a pathogen or prescribe a universal chemical treatment.