⭐ Asterina Starfish

Asterina starfish are tiny, usually benign hitchhikers found in most reef tanks. These small, irregularly-shaped stars are often the subject of debate in the hobby - some consider them harmless scavengers while others view them as potential coral pests. The truth is somewhere in between, and understanding when they become problematic is key.

📋 Quick Facts

Type	Small starfish (Asterinidae family)
Appearance	Small (1/4" - 1/2"), irregular arm count, various colors
Severity	Low - Usually harmless, occasionally problematic
Common Entry	Hitchhiker on live rock, coral frags
Treatment Difficulty	Easy - Simple biological control available

🔍 Identification

Asterina starfish are distinctive and easy to identify:

• Very small - Typically 5-15mm across
• Irregular arms - Often 5-6 arms of uneven length
• Variable color - White, cream, tan, brown, or greenish
• Flat body - Compressed, hugs surfaces closely
• Found on glass - Often seen on aquarium glass at night
• Asexual reproduction - Frequently missing/regenerating arms

Population Explosions

Asterina reproduce rapidly through fragmentation (dropping arms that grow into new stars). Populations often boom then crash naturally, typically correlated with available food sources.

🤔 Are They Harmful?

Usually Harmless

The majority of Asterina in reef tanks are beneficial scavengers:

• Eat detritus, uneaten food, and film algae
• Help clean glass and rocks
• Part of a healthy, diverse ecosystem
• Indicate good water quality when present

Potentially Problematic

Some individuals or populations can become pests:

• Coral eating - Rare individuals develop taste for coral tissue
• Zoanthid irritation - May irritate zoanthids, causing them to stay closed
• Coralline grazing - Large populations can consume coralline algae
• Aesthetic concern - Some hobbyists dislike the appearance of many small stars

Warning Signs

Watch for these indicators that Asterina are causing problems:

• White spots on coral where Asterina were sitting
• Corals remaining closed or retracted when stars are present
• Stars consistently found on same coral
• Visible tissue damage in star's feeding area

💊 Control Options

1. Do Nothing

Often the best approach:

• Populations typically self-regulate
• Boom and bust cycles are normal
• Provide beneficial scavenging
• Only intervene if actual damage observed

2. Harlequin Shrimp

The most effective biological control:

• Harlequin shrimp (Hymenocera elegans) eat ONLY starfish
• Will completely eliminate Asterina population
• Beautiful, interesting animals to observe
• Critical consideration: Must be fed starfish regularly after Asterina gone
• Will eat any starfish including expensive decorative species
• Often sold in mated pairs
• Can be temporarily housed, then rehomed/traded after job is done

3. Manual Removal

• Pick off with tweezers or fingers
• Best done at night when they're active on glass
• Remove whole stars - fragments regenerate
• Time-consuming for large populations
• Good option for maintaining low numbers

4. Wrasse Predation

Some wrasses will eat Asterina:

• Yellow Coris Wrasse - May eat small Asterina
• Melanurus Wrasse - Occasionally picks at them
• Not reliable as primary control
• Good for keeping populations in check

5. Reduce Food Source

• Reduce feeding to limit population growth
• Improve detritus export (better flow, cleaning)
• Run skimmer more aggressively
• Population will naturally decline with less food

🛡️ Prevention

• Quarantine live rock - Inspect and remove visible stars
• Dip coral frags - Pests often shake off during dipping
• Inspect purchases - Check frag plugs and bases
• Accept some presence - Complete prevention is nearly impossible

📊 Population Management

Population Level	Action
Few (1-10)	Monitor, no action needed
Moderate (10-50)	Monitor for coral damage, manual removal if desired
High (50-100+)	Manual removal or consider harlequin shrimp
Coral damage observed	Immediate removal of problem individuals, consider harlequin shrimp

❌ Common Mistakes

• Panicking over a few Asterina (they're usually fine)
• Adding harlequin shrimp without plan for feeding after Asterina gone
• Tearing Asterina apart (creates multiple new ones)
• Blaming Asterina for coral problems caused by other issues
• Removing all of them and losing beneficial scavenging

📚 Summary

Asterina starfish are generally harmless inhabitants that provide beneficial scavenging in reef tanks. Only take action if you observe actual coral damage or have aesthetic objections to large populations. When control is needed, harlequin shrimp are extremely effective but require commitment to feed after the Asterina are gone. For most tanks, a "wait and see" approach is best - populations typically regulate themselves over time.