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All problems
Moderate
Pest

Tiny black flies around plants (fungus gnats)

Small dark flies, 2–3 mm long, hopping around the base of plants and the top of the media.

Commonly affects: All hydroponic crops, worst on seedlings

What you'll see

  • Small black flies on, around, and above the media
  • Flies hop / walk more than they fly
  • Tiny white maggots in the top 1 cm of media
  • Seedlings stunted or dying — larvae eat fine roots

Likely causes

  • Wet, organic-rich media surface (especially coco)
  • Algae growth feeding the larvae
  • Over-watering top-fed systems
  • Flies brought in on new plants or contaminated media

How to fix it (step by step)

  1. 1Apply yellow sticky traps just above the canopy — kills the adults
  2. 2Top-dress media with 1 cm of dry sand or perlite to block egg-laying
  3. 3Seek advice on a registered larval-control treatment suited to the crop and follow its label
  4. 4Let the surface dry between feeds where possible
  5. 5Eliminate algae (see green slime above) — removes the food source

Stop it happening again

  • Cover reservoir and media surface to block light
  • Quarantine new plants for 1 week before adding them to your system
  • Avoid keeping the media surface constantly wet

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.

Further reading

These sources support general cultivation guidance, not verified Nana Organics product performance. Current NaO instructions take precedence over another brand’s feeding schedule.