Algae is a natural part of any aquarium ecosystem, but excessive growth signals an imbalance between light, nutrients, and the organisms consuming them.

Too much light is the most common trigger. Aquariums near windows receiving direct sunlight or running tank lights for more than 10 hours daily create ideal conditions for algae blooms. Reduce your photoperiod to six to eight hours using a timer, and move the tank away from direct sunlight if possible.

Excess nutrients fuel algae growth. Overfeeding is the primary source, as uneaten food decays into phosphate and nitrate that algae thrives on. Feed only what fish consume in two minutes and remove any visible leftovers. High nitrate levels from infrequent water changes also feed algae, so maintain a consistent water change schedule.

In planted tanks, an imbalance between light intensity, CO2, and fertilizer often causes specific algae types. Too much light without enough CO2 and nutrients for plants to use it gives algae the advantage. Balancing all three factors or reducing light to match available CO2 usually resolves the issue.

New tank algae blooms, including brown diatom algae on glass and decorations, are normal during the first few months. Diatoms typically fade on their own as the tank matures and silicates are depleted.

Algae-eating crew members help manage growth. Nerite snails, amano shrimp, otocinclus catfish, and siamese algae eaters consume various algae types and provide biological control alongside proper management.

Manual removal by scraping glass, trimming affected plant leaves, and vacuuming the substrate during water changes keeps algae in check while you address the underlying cause. Algaecides treat symptoms but do not fix the imbalance and can harm sensitive fish and invertebrates.