Green Hair Algae (Marine) Care Guide
Bryopsis sp. · Saltwater algae
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What Green Hair Algae (Marine) look like
Feathery, fern-like bright green filaments growing 2–10 cm from live rock. More structured and branching than freshwater hair algae. Often grows in dense mats that trap detritus.
Behavior & temperament
Aggressive nuisance algae indicating elevated phosphates and/or nitrates. Extremely persistent — can regrow from microscopic fragments. Traditional algae eaters often refuse it.
Behind the name
From Greek 'bryon' (moss) and 'opsis' (appearance), meaning moss-like.
Plan your tank
Check the numbers before you buy: tank volume, salinity, salt mix, water changes, and your ongoing care routine. Keeping reef? Start from the Saltwater & Reef hub.
Keep reading
How to quarantine new saltwater fish against marine ich, velvet, and brooklynella: the QT tank, treatments, timelines, and the buy-clean shortcut.
What every reef parameter means and where to keep it: salinity, temperature, pH, alkalinity, calcium, magnesium, nitrate, and phosphate.
Choose compatible fish: school sizes, swimming zones, aggression, temperature and hardness matching, and honest bioload math for a peaceful community.
Keeping Green Hair Algae (Marine)?
AquaLens identifies your fish and plants from a photo, tracks water chemistry, and flags health issues early — free on iOS and Android.