đŋ Hair Algae (Green Hair Algae)
Hair algae is one of the most common nuisance algae in reef aquariums. These green, filamentous strands can quickly cover rocks, substrate, and even corals if conditions favor their growth. While frustrating, hair algae is almost always a sign of excess nutrients and can be controlled through proper husbandry and targeted interventions.
đ Quick Facts
| Type | Green filamentous algae (various species) |
|---|---|
| Appearance | Green, hair-like strands, 0.5-4+ inches |
| Severity | Moderate - Unsightly, can smother corals |
| Common Causes | High nutrients, excess light, poor flow |
| Treatment Difficulty | Moderate - Requires addressing root causes |
đ Identification
Hair algae characteristics:
- Filamentous strands - Individual hair-like threads
- Green color - Bright to dark green
- Attached growth - Anchored to rocks, substrate, equipment
- Soft texture - Flows in current
- Pulls off - Can be manually removed (unlike turf algae)
Hair Algae vs. Similar Algae
| Type | Appearance | Texture | Removal |
|---|---|---|---|
| Hair Algae | Long green strands | Soft, flowing | Pulls off |
| Turf Algae | Short, dense mat | Tough, carpet-like | Difficult to remove |
| Bryopsis | Feathery, fern-like | Delicate fronds | Grows back from fragments |
| GHA (long) | Very long strands | Wiry | Pulls off easily |
â ī¸ Common Causes
Nutrient Issues
- High phosphates - Primary driver of hair algae
- Elevated nitrates - Fuels algae growth
- Overfeeding - Excess food becomes algae fertilizer
- Overstocking - More fish = more waste
- Inadequate export - Skimmer undersized or poorly tuned
- Tap water - Contains phosphates and silicates
Other Factors
- Excessive lighting - Too intense or too long photoperiod
- Poor flow - Stagnant areas accumulate nutrients
- Old light bulbs - Spectrum shift favors algae
- New tank syndrome - Immature biological filtration
- Die-off events - Dead organisms release nutrients
đ Treatment Options
1. Address Nutrient Sources (Essential)
This is the most important step:
- Test nitrates and phosphates - know your numbers
- Use quality RODI water for all top-off and water changes
- Reduce feeding - only what fish consume in 2-3 minutes
- Increase water change frequency
- Upgrade or tune protein skimmer
- Check for hidden die-off (dead snail, etc.)
2. Phosphate Reduction
- GFO (Granular Ferric Oxide) - Run in reactor or media bag
- Phosphate remover pads - In filter or sump
- Lanthanum chloride - Liquid phosphate remover (use carefully)
- Target phosphate below 0.03 ppm for control
- Don't crash phosphates too fast - can shock corals
3. Manual Removal
- Pull/twist algae off rocks by hand
- Use toothbrush to scrub rocks
- Siphon removed algae during water change
- Remove rocks for cleaning if heavily covered
- Do regularly - disrupts growth cycle
4. Biological Controls
Clean-up crew additions that eat hair algae:
- Emerald crabs - Excellent hair algae consumers
- Sea hares - Voracious algae eaters (temporary)
- Turbo snails - Mexican turbos are especially effective
- Trochus snails - Steady grazers
- Tangs - Many species love hair algae (need large tank)
- Foxface/Rabbitfish - Excellent algae eaters
- Lawnmower Blenny - Grazes on shorter algae
5. Competing Algae (Refugium)
- Grow macroalgae (chaeto) in refugium
- Competes with hair algae for nutrients
- Harvest regularly to export nutrients
- Run refugium light opposite of display
6. Reduce Light
- Shorten photoperiod to 6-8 hours
- Reduce intensity if possible
- Replace old bulbs (spectrum shift)
- Increase blue, reduce white spectrum
7. Chemical Treatments
- Vibrant - Bacterial product, effective for many
- Fluconazole - For Bryopsis specifically (prescription needed)
- Hydrogen peroxide - Spot treatment (careful near corals)
- Chemical treatments work best combined with nutrient reduction
8. Improve Flow
- Add or reposition powerheads
- Eliminate dead spots
- Algae struggles in high-flow areas
- Random/wave patterns better than laminar flow
âąī¸ Treatment Timeline
| Week | Actions |
|---|---|
| 1 | Test nutrients, start GFO, reduce feeding, manual removal |
| 2 | Add emerald crabs/turbos, continue manual removal |
| 3-4 | Evaluate nutrient reduction, adjust lighting if needed |
| 5-8 | Continue protocol, consider Vibrant if no improvement |
| 8+ | Maintain low nutrients, gradual improvement expected |
đĄī¸ Prevention
- Use RODI water exclusively
- Don't overfeed
- Maintain proper nutrient levels (not zero, not high)
- Keep adequate clean-up crew
- Run refugium with macroalgae
- Regular water changes
- Properly sized protein skimmer
- Good flow throughout tank
â Common Mistakes
- Only doing manual removal without addressing nutrients
- Using tap water (contains phosphates)
- Crashing nutrients too fast (stresses corals)
- Expecting instant results (takes weeks to months)
- Adding more light to "outcompete" algae (makes it worse)
- Relying solely on clean-up crew without nutrient control
- Giving up too soon
đ Summary
Hair algae is fundamentally a nutrient problem. While manual removal and biological controls help manage it, lasting success requires reducing the nutrient levels that fuel algae growth. Test your water, use RODI, don't overfeed, and run GFO if phosphates are elevated. Combine this with a good clean-up crew (emerald crabs and turbo snails are stars) and patience. Most tanks see significant improvement within 4-8 weeks of consistent effort. Remember - some algae is natural and healthy; the goal is control, not complete elimination.