Algae Turf Scrubber: A Guide
An algae scrubber grows algae on a lit screen to absorb nitrate and phosphate, exporting nutrients when the algae is harvested.
Overview
An algae scrubber, or algae turf scrubber, is a device that deliberately grows algae on a screen under intense light. The growing algae consume nutrients from the water, and removing the algae exports those nutrients from the system. It is used as a chemical-free nutrient control method in both saltwater and freshwater tanks.
How it works
Water is moved rapidly over a rough, brightly illuminated surface, which encourages algae to grow vigorously. Modern designs use either an up-flowing stream of air bubbles or a gravity-driven waterfall to create turbulence over the screen. Because the algae grows inside the filter, it competes with and starves out nuisance algae in the display.
Nutrients removed
- Nitrate and nitrite
- Phosphate
- Ammonia and ammonium
- Some metals such as copper
Lighting and growth
Strong illumination is essential, and many designs use red and other LED light. Green hair algae is generally preferred over brown turf algae because, kept under about 20 mm thick, it lets light and water reach the screen and grows and absorbs nutrients faster. A scrubber typically takes several months to become well seeded and fully effective.
Harvesting and nutrient export
The algae is removed roughly every 7 to 21 days, or when growth turns black, fills the screen, or when nutrient levels in the water rise. Physically removing the algae is what actually exports the absorbed nitrate, phosphate and other nutrients from the aquarium.
Limitations
A scrubber needs space, a dedicated light, and regular harvesting to keep working. If algae is left to grow too thick it weakens, and the bright light can be visible if the unit is not enclosed. It is a slow, gradual method rather than an instant fix.