Step-by-step
Step 1: Identify the algaeBrown dust = diatoms (new tank). Green hair = GHA (excess phosphate). Bright green tufts = filamentous algae. Bubble algae = saltwater bubble algae (Valonia). Fern-like = bryopsis. Red/brown slime = cyanobacteria.
Step 2: Test phosphate + nitrateReef target: phosphate 0.03-0.05 ppm, nitrate 5-10 ppm. Higher = nutrient excess fueling algae. Lower (0 ppm) = nutrient starvation that drives dinoflagellates.
Step 3: Manual removal firstMagnet glass scraper for surfaces. Toothbrush for rocks. Pull out hair algae by hand during water changes (lift and scoop).
Step 4: Reduce photoperiodCut from 10 hours to 6-8 hours during outbreak. Restore once cleared. Algae growth is light + nutrient driven; cut both for 2 weeks.
Step 5: Add a CUCSaltwater: turbo + Mexican turbo snails for GHA. Emerald crabs for bubble algae. Reef-safe wrasse (sixline) for AEFW. Freshwater: nerite snails + amano shrimp + otocinclus.
Step 6: Reduce nutrientsSaltwater: GFO in a reactor for phosphate. Bio-pellets or vodka dosing for nitrate. Freshwater: water changes + reduce feeding.
Step 7: Treat persistent algaeBryopsis: elevate Mg to 1600-1800 ppm with Tech-M for 4-6 weeks. Cyano: ChemiClean (Boyd) chemical treatment. Dinos: raise nutrients + UV sterilizer + lights-out 3 days.
Frequently asked questions
What causes aquarium algae?
Excess nutrients (phosphate + nitrate from feeding + waste) combined with light. The right amount of either alone is fine; the combination drives blooms.
How do I prevent algae?
Stable nutrients (not too high, not too low), balanced photoperiod (6-10 hours), strong CUC, regular maintenance. Run RODI not tap water (tap water has phosphate).
Can I use bleach to clean algae from rocks?
YES for dry rocks BEFORE placement - 10:1 water-to-bleach soak, rinse thoroughly, sun-dry 48 hours. NEVER use bleach on rocks while in a tank with livestock.