Algae on or around your plant can lead to further problems, symptoms could look like pH fluctuation.
When growing in hydro or aeroponics, use all black or opaque equipment, cleaned, to discourage growth. Water temperature should be kept around 22C. Higher temperature promotes algae growth.
To remove algae you can use a hydrogen peroxide solution, dilute 29% at 1ml per gallon. Dilution must be at least 1:10 times to avoid acidic damage to the plant.
• Algae can show up when a plant is being overwatered, so hold off on watering until the plant is dry and remove the algae.
• Add a tarp/cover over your soil when not watering.