FastAquatics
Step-by-step how-to

How to remove algae from your aquarium

Step-by-step algae removal protocol. Diatoms, hair algae, bubble algae, bryopsis, cyanobacteria - identification and treatment.

Beginner7 steps14 days

What you'll need

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.

Related guides + tools

Browse all how-to guides, calculators, setup guides, or the disease database for related help.

Aquarium-keeping fundamentals

Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.

Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.

Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.

Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.

Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.

Frequently asked questions

How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.

What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.

How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.

Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.

Related resources

Saltwater livestock · Freshwater livestock · Coral catalog · Care library · Q&A library (222) · Glossary (127) · Disease database (50) · Calculators (29) · Interactive tools (7) · Husbandry deep-dives · DIY projects · State legality directory