🔴 Cyanobacteria (Red Slime Algae)

Cyanobacteria, commonly called "cyano" or "red slime algae," is actually not an algae at all - it's a photosynthetic bacteria. This slimy, often red or maroon coating can quickly cover sand, rocks, and corals if conditions favor its growth. While unsightly and potentially harmful to corals, cyano is usually a symptom of underlying water quality issues that are relatively easy to address.

📋 Quick Facts

Type	Photosynthetic bacteria (not true algae)
Appearance	Slimy red, maroon, brown, or green sheets
Severity	Moderate - Smothers surfaces, indicates water quality issues
Common Causes	High nutrients, poor flow, old bulbs, overfeeding
Treatment Difficulty	Easy to Moderate - Address root causes

🔍 Identification

Cyanobacteria has distinctive characteristics:

• Sheet-like growth - Forms coherent mats that peel off in sheets
• Slimy texture - Slippery, mucus-like feel
• Color varies - Red/maroon most common, but can be green, brown, or black
• Bubbles underneath - Oxygen bubbles collect under the mat
• Distinctive smell - Musty, earthy odor when disturbed
• Rapid regrowth - Returns within days of removal if cause not addressed
• Prefers low flow areas - Accumulates in dead spots

Cyano vs. Similar Organisms

Feature	Cyanobacteria	Dinoflagellates	Hair Algae
Texture	Slimy sheets	Snotty strings	Hairy/fuzzy
Removal	Peels off in sheets	Stringy residue	Must be pulled
Smell	Musty/earthy	Minimal	None
Color	Red/maroon typical	Golden brown	Green

⚠️ Common Causes

• Elevated nutrients - High nitrates and/or phosphates
• Poor water circulation - Dead spots with stagnant water
• Old light bulbs - Spectrum shift favors cyano growth
• Overfeeding - Excess organics fuel bacterial growth
• Inadequate filtration - Insufficient biological filtration
• Infrequent water changes - Buildup of dissolved organics
• Silicates in source water - Can contribute to outbreaks
• New tank syndrome - Immature biological filtration
• Detritus accumulation - Rotting debris feeds cyano

💊 Treatment Options

1. Address Root Causes (Most Important)

Without fixing underlying issues, cyano will always return:

Improve Water Quality

• Test nitrates and phosphates - reduce if elevated
• Increase water change frequency
• Use quality RODI water
• Run GFO if phosphates are high
• Don't overfeed - feed only what fish consume in 2-3 minutes
• Remove uneaten food promptly

Improve Flow

• Add or reposition powerheads
• Eliminate dead spots where cyano accumulates
• Consider wave makers for variable flow
• Clean powerhead impellers for maximum output

Address Lighting

• Replace old bulbs (T5, MH) - spectrum shifts over time
• Reduce photoperiod temporarily (8 hours max)
• Ensure lights aren't too intense for tank's nutrient load

2. Manual Removal

• Siphon out during water changes
• Use airline tubing for precision removal
• Turkey baster to blow off rocks before siphoning
• Remove as much as possible each time
• Vacuum substrate in affected areas

3. Increase Biological Competition

• Add beneficial bacteria products (Microbacter7, Dr. Tim's)
• Establish macroalgae in refugium
• Increase pod population
• A healthy, diverse microbiome outcompetes cyano

4. Chemical Treatments

Use as a last resort or jumpstart while addressing causes:

Chemiclean / Red Slime Remover

• Erythromycin-based antibiotic treatment
• Very effective at killing cyano
• Follow directions exactly
• Increase aeration during treatment (reduces oxygen)
• Run carbon after treatment
• Warning: Can affect beneficial bacteria; causes die-off that spikes ammonia
• Cyano returns if root cause not addressed

Vibrant

• Bacterial competition product
• Reef-safe, doesn't use antibiotics
• Takes longer but gentler approach
• Dose according to instructions

Hydrogen Peroxide (Spot Treatment)

• 3% H2O2, 1ml per gallon in affected area
• Turn off flow, apply directly to cyano
• Wait 5 minutes, resume flow
• Use sparingly - can affect corals

5. Blackout

• 3-day complete darkness
• Cover tank entirely
• Maintain circulation and filtration
• Less effective for cyano than dinoflagellates
• May stress corals

🐟 Biological Controls

Few animals reliably eat cyano, but some help:

• Cerith snails - May graze on thin cyano
• Nassarius snails - Disturb substrate, limiting growth
• Turbo snails - Occasionally eat cyano on rocks
• Sea hares - Some species consume cyano
• Note: No animal is a reliable cyano solution

⏱️ Treatment Timeline

Week	Actions
1	Test water, improve flow, reduce feeding, manual removal
2	Continue manual removal, increase water changes
3	Evaluate progress, consider chemical treatment if no improvement
4+	Maintain good practices, cyano should decrease

🛡️ Prevention

• Maintain good water quality with regular testing
• Perform regular water changes (10-20% weekly)
• Don't overfeed
• Ensure adequate flow throughout tank
• Replace light bulbs on schedule
• Remove detritus regularly
• Use quality source water
• Maintain healthy refugium

❌ Common Mistakes

• Using chemical treatment without fixing root causes
• Reducing flow to avoid spreading (makes it worse)
• Ignoring the problem hoping it goes away
• Not increasing aeration during Chemiclean treatment
• Confusing cyano with other organisms
• Panicking - cyano is very common and manageable

📚 Summary

Cyanobacteria is one of the most common issues in reef keeping, but it's also one of the most manageable. The key is understanding that cyano is a symptom of underlying conditions - typically high nutrients, poor flow, or both. Address these root causes and the cyano problem will resolve. Chemical treatments can provide quick relief but should be combined with correcting the underlying issues, or the cyano will simply return. With good husbandry practices, cyano outbreaks are easily prevented.