Coco Worm Care and Feeding

Unlike some other marine worms, coco worms do not have an operculum (trap door) at the tube opening. This means they cannot seal themselves in, so you must keep them fully submerged at all times-even during transport or maintenance.

The worm's crown is covered in feather-shaped rays that collect microscopic food particles from the water. Tiny hair-like structures called cilia move captured food particles down grooves in the rays toward the worm's mouth. When frightened or stressed, the worm retracts its entire crown instantly into the protective tube. If severely stressed, it may even shed its crown, though a new one will regenerate over time.

Proper Placement and Tank Setup

Positioning your coco worm correctly is one of the most important factors in keeping it healthy and feeding actively.

Placement location:

• Place the coco worm in a shaded or semi-sheltered area of your rockwork

• If placing on the sand bed, gently bury the hard tube so the crown points upward
• Alternatively, nestle the tube into a hole or crevice in the live rock where it won't be disturbed
• The crown should face into a gentle light current that brings food particles toward it

Why location matters:
A well-positioned coco worm will spend most of its time with its crown fully extended, actively feeding. Poor placement-such as putting the crown in direct, forceful water flow or in total darkness-will cause the worm to keep retracting and miss feeding opportunities.

Since coco worms require calcium carbonate to build and maintain their hard tubes (similar to stony corals), place them in a well-maintained reef tank where you're already monitoring and supplementing calcium and carbonate levels.

How to Feed Coco Worms: Diet and Frequency

Coco worms are filter feeders that naturally consume phytoplankton, zooplankton, bacteria, and fine detritus suspended in the water column. In many reef tanks, especially those with live rock and an established population of small organisms, these worms may receive enough food from the water without supplemental feeding. However, targeted feeding ensures they stay well-nourished and continue to thrive.

Natural food sources in your tank:

• Phytoplankton and zooplankton in the water

• Bacteria
• Organic detritus and particulate matter
• Microorganisms that colonize live rock and substrates

Supplemental feeding options:

• Prepared liquid phytoplankton products
• Frozen phytoplankton

• Liquid zooplankton supplements
• Specialized filter-feeder foods

Feeding frequency:

• In heavily stocked reef tanks with many filter feeders (corals, bivalves, other worms): feed daily
• In lightly stocked tanks with few filter feeders: feed 2-3 times per week
• Start conservatively and adjust based on water quality; overfeeding can foul your water and stress corals

How to feed without startling the worm:
Use a turkey baster to gently blow food into the water current that flows toward the crown-not directly at it. The worm will naturally spread its crown to intercept food particles as they drift by. If you direct food straight at the crown, the worm will immediately retract into its tube and won't feed. Work with the current, not against it.

Calcium and Carbonate Requirements

One of the most commonly overlooked aspect of coco worm care is their need for adequate calcium and carbonate alkalinity. These worms build their impressive hard tubes continuously, and without sufficient calcium carbonate in the water, they cannot grow or maintain their tubes properly.

What you need to do:

• Supplement your reef tank with calcium and carbonate (alkalinity) regularly
• Test your water frequently to ensure calcium levels stay in the optimal range for stony corals (typically 400-450 ppm)
• Use quality water testing to monitor carbonate hardness (dKH) as well
• If your tank houses both corals and coco worms, maintain levels suitable for both

Without these supplements, coco worms may weaken, stop feeding, or fail to grow their tubes properly. Check your reef tank's calcium and carbonate levels before adding a coco worm and keep them monitored as part of your routine maintenance.

Tank Mates and Compatibility

Coco worms are peaceful and compatible with virtually all corals and invertebrates in a reef aquarium. They pose no threat to fish, corals, or other creatures.

Safe to keep with:

• All stony and soft corals
• Fish of any species
• Other invertebrates (sea stars, urchins, snails, hermit crabs)
• Other filter feeders, including soft corals and other fan worms

Watch out for crabs:
Some crabs may persistently pester a coco worm, causing it to stay retracted and unable to feed properly. If you notice a crab repeatedly bothering your worm and it remains hidden for extended periods, remove the crab to keep your worm healthy. Otherwise, coco worms and crabs can coexist peacefully in most setups.

Transporting and Acclimating Coco Worms

Because coco worms lack an operculum (trap door), they're vulnerable to desiccation and air exposure. Proper transport is critical.

Transport steps:

• Fill a fish bag with water from your aquarium (the source tank or LFS system)
• Gently place the coco worm into the bag
• Keep the worm completely submerged throughout transport
• Never lift it out of water or expose the tube to air
• Transport as quickly as possible to avoid temperature and pH shock

Acclimation:
Once home, acclimate your coco worm using standard saltwater invertebrate acclimation. Float the sealed bag in your tank for 15-20 minutes to equalize temperature, then gradually add small amounts of tank water to the bag over another 15-20 minutes before gently releasing the worm into its placement location.

Hardiness and Growth

Coco worms are hardy, low-maintenance creatures that quickly become favorites in established reef tanks. Their bright, feathery crowns add striking visual interest, and they're nearly impossible to kill once they're settled and feeding regularly.

Their hard tubes can grow up to 24 inches long and often develop interesting bends and spiral patterns along their length. These distinctive tubes are as much a part of the worm's beauty as the colorful crown itself. Over time, a healthy coco worm becomes a permanent fixture of your aquascape, growing and feeding quietly in its chosen spot.

Other Popular Fan Worms for Reef Tanks

If you fall in love with coco worms, you may be interested in their relatives-other stunning fan worms that thrive in reef aquariums.

Hawaiian Feather Duster (Giant Feather Duster)

The Hawaiian Feather Duster is a larger species that can grow up to 7 inches long, with a crown reaching 7 inches in diameter. The crown typically displays earthy tones-tan with dark brown bands, or tan or brown with white bands. While less colorful than coco worms, these worms add a unique, natural beauty to the reef and are just as hardy and easy to care for. They benefit from the same feeding, placement, and calcium supplementation as coco worms.

Dwarf Feather Duster

For smaller tanks or those seeking a more subtle option, the Dwarf Feather Duster grows only up to 4 inches long. The tube is light brown, and the crown can display vibrant color combinations: red and white, pink and white, lime green, or white and yellow. These smaller worms have the same care requirements as coco worms but take up less space and are ideal for tanks where room is limited.