Blue Velvet Nudibranch (Casella atromarginata)

Blue Velvet Nudibranch (Casella atromarginata)

Blue Velvet Nudibranch (Casella atromarginata)

The Blue Velvet Nudibranch (Casella atromarginata) known to tropical fish keeping enthusiasts as the Blue Velvet Sea Slug or Head Sheild Sea Slug is found in the Western Pacific and Indian Oceans.

The Blue Velvet Nudibranch is a peaceful, mostly nocturnal species that spends all of its waking hours searching out and feeding on flatworms.  They may secrete trace amounts of poisonous toxins as a defense mechanism when threatened and should not be housed with aggressive predators that may view them as a meal.

Blue Velvet Nudibranch (Casella atromarginata

Blue Velvet Nudibranch (Casella atromarginata

The Blue Velvet Nudibranch has a has a hammer shaped head and a beautiful velvety black body with electric blue lines highlighting the edges of the body and the middle of the head.

Although Casella atromarginata have a relatively short life expectancy in an aquarium environment and their care is suggested only for expert aquarists, they are voracious eaters of flatworms and are highly recommended by tropical fish keeping enthusiasts if you have a flatworm problem in your reef system.

The Blue Velvet Nudibranchs is best housed in an established reef tank of at least 20 gallon capacity with plenty of live rock, sand, and flatworms.    They do exceptionally well in established reef tanks and are reef safe, however, lacking a substantial colony of flatworms, they will require supplemental feedings.    Because nudibranchs can get sucked up into aquarium pump intakes, drains, and powerheads in reef aquariums,  it’s a good idea to screen them off.

Like most invertebrates, the Blue Velvet Nudibranch requires stable water quality and is very sensitive to rapid changes in water conditions.  They are especially sensitive to higher levels of nitrates and cannot tolerate any amount of copper in the system.  When purchased they should be slowly drip acclimated with the lights off when introduced into the tank.

In established reef aquariums, regular spawning often occur when Casella atromarginata are maintained together, however, there has not been a great success rate reported by aquarists in raising the larvae.

The Blue Velvet Nudibranch is a specialty feeder that thrives on flatworms as their primary diet.  They feed on the flatworms using their tube like proboscis to suck them up and in an aquarium environment are a great natural alternative for flatworm control.   Lacking a steady diet of flatworms in their diet, they will usually not eat enough of anything else to thrive and will slowly starve without their primary food source.

Because of this and their short life span, only expert tropical fish keeping enthusiasts should attempt to maintain this species.

The Blue Velvet Nudibranch (Casella atromarginata) is available to tropical fish keeping enthusiasts from specialty shops and online from a variety of sources at an approximate purchase size of 1″ to 2″ at reasonable prices.

Blue Velvet Nudibranch (Casella atromarginata)

Blue Velvet Nudibranch (Casella atromarginata)







Minimum Tank Size: 20 gallons
Aquarium Type: Established Reef
Care Level: Moderate
Temperament: Peaceful
Aquarium Hardiness: Relatively hardy
Water Conditions: 72-78°F, dKH 8 to 12, pH 8.1-8.4, sg 1.023-1.025
Max. Size: 2.75″
Color Form: Black, Blue
Diet: Specialty Carnivore
Compatibility: Reef Compatible
Origin:  Western Pacific, Indian Ocean
Family: Chromodorididae
Lifespan: Unkonwn
Aquarist Experience Level: Expert Only

Leave a Reply

Saltwater Fish

Featuring Clownfish

Aquarium Supplies

On-Sale Aquarium Supplies!

Saltwater Holiday Specials

Tropical Fish Keeping – Categories