How to Get Rid of Aquarium Algae

Almost every algae problem comes down to one imbalance: more light and nutrients than your plants and animals can use up. Once you see it that way, the fixes are obvious and the chemicals become unnecessary.

1. Cut the light

Light is the fuel, so it is the first lever:

• Shorten the photoperiod to 6 to 8 hours a day, on a timer for consistency.
• Move the tank out of direct sunlight, which is a relentless algae driver you cannot control.
• If you run a bright planted light, dial the intensity down rather than leaving it at full.

2. Cut the nutrients

Algae feeds on the same nutrients as plants, especially nitrate and phosphate from waste and food:

• Feed less; uneaten food is pure algae fuel.
• Do regular water changes to export nutrients, which is also how you lower nitrates.
• Avoid overstocking, and remove decaying leaves and debris.

3. Add cleanup

Once the inputs are under control, remove what is there and let helpers keep it down. Scrape the glass, wipe or toss badly affected decor, and consider algae-grazing animals suited to your tank, such as nerite snails, otocinclus or amano shrimp. They graze algae but cannot outpace a tank that still has too much light and food.

Match the fix to the algae

Type	Usual cause	First fix
Green water	Excess light and nutrients	Blackout, cut light, water changes
Green spot on glass	Normal, some light	Scrape; often cosmetic
Brown (diatoms)	New tank, silicates	Usually fades as the tank matures
Black beard	Unstable CO2, low flow, excess light	Cut light, improve flow

Chemical algaecides exist, but they treat the symptom and can harm plants and animals. Fix the light and nutrients and the algae fades on its own. If your water is cloudy rather than algae-covered, that is a different issue covered in why is my aquarium water cloudy.