Why Low-Tech Tanks Get Algae
Algae blooms when nutrients exceed plant uptake capacity. In low-tech tanks, plant uptake is naturally low because growth is slow without CO2.
Trigger combinations: too much light + too few plants + too much nitrate from overfeeding.
Lighting Adjustment
Reduce photoperiod to 6 hours per day. If algae persists, reduce to 5 hours.
If using high-output LED, install a dimmer or raise the fixture 6–12 inches above the tank.
Plant Mass
Heavy planting outcompetes algae for nutrients. Add fast-growing plants: hygrophila, water wisteria, vallisneria, frogbit (floating).
Floating plants are particularly effective — they shade the tank and absorb nutrients before algae can.
Cleanup Crew
Amano shrimp: best general algae eater. 1 per 5 gallons.
Nerite snails: eat hard algae from glass and rocks. Will not breed in freshwater.
Otocinclus: gentle, eat soft green algae from leaves. School of 4–6.
Siamese algae eater: eats black brush algae (rare). Adult-only behavior.
Chemical Treatment
Excel (Seachem): liquid carbon, kills BBA at 2× normal dose.
Hydrogen peroxide spot treatment: 3% drugstore peroxide, 1 ml per gallon, applied directly to BBA-covered surfaces with a syringe (tank powered off, wait 5 minutes).
Algaecides: avoid — kill plants and fish.
Algae Type Guide
Green dust algae: light too long. Reduce photoperiod.
Green hair algae: too many nutrients. Water change, reduce feeding.
Brown diatoms: new tank phase. Will resolve naturally in 4–6 weeks.
Black brush algae (BBA): inconsistent CO2 / liquid carbon. Dose Excel.
Blue-green algae (cyanobacteria): low nitrate, dirty substrate. Vacuum, water change, reduce light.