Coral Tank Blackout Shading Technique | Practical Methods to Eliminate Cyanobacteria and Algae
Blackout (complete light deprivation) is an effective technique to eliminate cyanobacteria and algae that proliferate in coral tanks. This guide thoroughly explains the correct procedures, duration, and risk management for corals.
Key Takeaways
Blackout (complete light deprivation) is an effective technique to eliminate cyanobacteria and algae that proliferate in coral tanks. This guide thoroughly explains the correct procedures, duration, and risk management for corals.
Related Species
What is Blackout?
Blackout is a reset technique where a tank is completely shaded for several days to kill cyanobacteria (blue-green algae) and certain types of algae that depend on photosynthesis. Since light is a lifeline in coral tanks, this technique carries risks, but when executed correctly, its effectiveness is tremendous.
Cyanobacteria manifest as a reddish-purple slimy coating on substrate, live rock, and the base of corals. If left untreated, it can lead to oxygen depletion and coral suffocation. Blackout is effective in situations where algae-eating organisms and water changes cannot keep pace.
What Types of Algae and Cyanobacteria Does It Work On?
Blackout is particularly effective on the following types:
- Cyanobacteria: Red-purple membrane-like growth. High photosynthetic capacity but weak against light deprivation. Dies within 3–4 days.
- Some green algae: Filamentous green algae and spot-forming algae. Growth is halted by light deprivation.
- Brown algae (diatoms): Common in early setup stages but can be reset with blackout.
Conversely, dinoflagellates (dinos) can sometimes backfire. Since certain species favor dark conditions, species identification beforehand is necessary.
Preparation Before Implementation
Pre-implementation preparation for safe blackout execution is extremely important.
1. Water Quality Check
Measure NO3, PO4, KH, Ca, and Mg, and adjust them to normal ranges before blackout. Since water quality testing is difficult during blackout, record the initial values.
2. Verify Coral Condition
Stressed or newly introduced corals have low tolerance to light deprivation and should be isolated beforehand. Healthy corals can tolerate 3–4 days of blackout, but SPS corals require particular care.
