What is a Refugium and Do I Need One?
Quick Answer
A refugium is a separate compartment in your sump that grows macroalgae and pods for natural filtration. While not essential, refugiums help reduce nitrates, stabilize pH, and produce live food for your tank.
A refugium is a dedicated section of your sump (or a separate chamber) where you grow macroalgae, cultivate copepods, and provide a protected habitat for beneficial organisms. Think of it as a "refuge" where helpful creatures thrive.
What a Refugium Does
Nutrient Export
Macroalgae like chaetomorpha absorbs nitrates and phosphates as it grows. When you harvest the algae, you physically remove those nutrients from your system—similar to how a protein skimmer exports organics.
Copepod Production
Refugiums are breeding grounds for copepods and other microfauna. These tiny crustaceans naturally migrate to your display tank, providing free live food for fish and corals.
pH Stabilization
Running your refugium light on a reverse cycle (lights on when display is off) keeps photosynthesis going 24/7. This helps stabilize pH swings between day and night.
Do You Need a Refugium?
Not everyone needs one. Consider a refugium if:
- You're battling persistent nitrate or phosphate issues
- You want to grow a natural copepod population
- Your pH drops significantly at night
- You prefer natural filtration methods
- You keep finicky fish that benefit from live food (mandarins, etc.)
You might skip a refugium if:
- Your parameters are already stable
- You have limited sump space
- You prefer other nutrient export methods (GFO, carbon dosing)
Setting Up a Refugium
What You Need
- Macroalgae: Chaetomorpha is the most popular choice
- Lighting: A simple grow light (18-24 hours or reverse photoperiod)
- Copepod starter: Live copepods to seed the population
- Flow: Gentle flow to tumble the algae
Starter Kits
Many sellers offer refugium starter kits that include chaeto and copepods together—an easy way to get started.
Refugium Maintenance
- Harvest algae: Remove excess growth every few weeks
- Clean light: Wipe off salt creep periodically
- Add pods: Reseed occasionally if population drops
- Monitor growth: Healthy chaeto stays green and grows visibly
Track your nitrate and phosphate trends with the ReefBay app to see the impact your refugium makes on water quality.
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