Reef Tank Algae Guide: Identifying and Eliminating Every Type

Every reef tank goes through algae phases. The good news: each type has a known cause and a known fix. Here is how to identify what you are dealing with and the protocol that actually works.

Diatoms (brown dust)

Normal in new tanks. Lasts 2–6 weeks as silicates from new sand and rock are consumed. No action required — cleanup crew handles it.

Cyanobacteria (red slime)

Caused by stagnant flow and nutrient imbalance. Increase flow, blackout 3 days, dose ChemiClean as last resort.

Green hair algae (GHA)

Phosphate driven. Manually remove, run GFO, increase nutrient export via skimming and water changes.

Bryopsis

Tough, feathery green. Use Fluconazole treatment over 14 days — coral safe.

Dinoflagellates

Snotty brown strings with bubbles. Raise nutrients, dose live phytoplankton, UV sterilize.

Track parameters with the Water Parameter Tracker.