Green slime or algae on the medium, roots or in the reservoir

Likely causes, most likely first

Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.

1. LikelyAlgae from light reaching wet surfaces or the reservoir

   Root zoneLow urgencyRead: How do I stop algae in my reservoir or on my medium?

   Fix: Block all light from reservoirs, tubing and the medium surface (opaque lids, covers on rockwool). Clean surfaces between runs. Algae competes for oxygen and feeds gnats and shore flies.

   Recovery: No new green growth within 1-2 weeks of light-proofing.

   How to confirm it

   • Look at the roots. Hydro: lift the net pot and look at the root mass in good white light. Containers: tip the plant out with a hand over the medium and look at the edges and bottom of the root ball. Healthy roots are white to cream with fine fuzzy tips. Brown roots whose outer layer slides off between the fingers leave a bare thread: rot. Firm, evenly tan roots with white tips in coloured solution are staining.

Look for

Green film on rockwool, coco surface, tubing or reservoir walls; note any light leaks into the reservoir..