How to Manage Cyanobacteria in your Reef Aquarium

Cyanobacteria (also called “cyano” or “red slime algae”) is a common nuisance in reef aquariums. It forms slimy, mat-like sheets over rocks, sand, and corals, and can smother marine life if left unchecked. Here’s a multi-step approach to getting rid of cyanobacteria:

1. Identify the Root Cause

Cyanobacteria thrive in environments with:

• High nutrients (nitrates and phosphates)
• Poor water circulation and flow
• Excess light (especially aged bulbs with shifted spectrum)

Addressing these root causes is key to long-term success.

2. Manual Removal

• Siphon the Cyano:
  During water changes, use a hose to vacuum up the cyano mats from rocks and sand.
• Do this gently to avoid spreading it further in the tank.
• Clean Filter Media:
  After siphoning, rinse or replace mechanical filters to remove dislodged cyano cells.

3. Improve Water Quality

• Lower Nutrients:
• Nitrate: Keep levels <5 ppm.
• Phosphate: Maintain levels <0.03 ppm.
• Use protein skimmers and filter socks to remove waste more efficiently.
• Consider biopellets, GFO (granular ferric oxide), or phosphate removers to reduce excess phosphates.
• Perform weekly water changes of 10–20% until the problem is under control.
• Rinse Frozen Foods:
  Thaw frozen foods in RO/DI water to remove excess nutrients before feeding.

4. Increase Flow and Circulation

• Boost Flow:
  Install or adjust powerheads or wave makers to ensure proper circulation. Cyanobacteria tend to grow in low-flow areas.
• Avoid Dead Spots:
  Redirect flow towards areas where cyanobacteria collect to prevent it from settling.

5. Optimize Lighting

• Reduce Light Intensity/Duration:
• Cut back on lighting periods by 1–2 hours a day temporarily.
• Avoid leaving lights on longer than 8–10 hours daily.
• If you’re using older bulbs, replace them, as spectrum shifts may promote cyano growth.

6. Use Beneficial Bacteria and Carbon Dosing

• Dose Bacteria:
  Products like MicroBacter7, Dr. Tim's, or FritzZyme can outcompete cyano by introducing beneficial bacteria.
• Carbon Dosing (e.g., Vinegar or Vodka):
  Helps promote bacterial populations that consume nitrate and phosphate, though it requires careful dosing to avoid imbalances.

7. Chemical Treatments (With Caution)

• Use Cyano Treatments:
  Products like Chemiclean or Blue Life Red Slime Remover are effective but should be used cautiously. Important Steps:
1. Turn off your protein skimmer (it will overflow during treatment).
2. Increase aeration with air stones or additional pumps to prevent oxygen depletion.
3. Follow the instructions carefully and perform a water change after treatment.

8. Add Clean-Up Crew (Cuc)

• Some invertebrates may help control cyano by grazing, although they are not a complete solution.
• Cerith snails and Nassarius snails help keep sandbeds clean.
• Conchs and sea hares may consume cyanobacteria in some cases.

9. Monitor and Prevent Future Outbreaks

• Test water weekly to track nitrate and phosphate levels.
• Maintain consistent water changes and avoid overfeeding.
• Quarantine new livestock and corals to prevent introducing cyano from other tanks.

By following these steps, you can get cyanobacteria under control while improving the overall health of your reef system. The key is consistency—maintaining good water quality and flow will prevent future outbreaks.