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Marine Invertebrate of the Month
Issue: March 2010

Holothuria edulis

LESSON 1830

IOM T 0310

Bob Goemans

Common Names: Edible cucumber, sea cucumber, pink fish

Phylum: Echinodermata

Class: Holothuroidea

Order: Aspidochirotida

Family: Holothuriidae

Range: Tropical Indo-West Pacific: Maldives, India, Philippines, East Indies, South China Sea, southern Japan, and northern Australia

Natural Environment: This pink and black sea cucumber attains a length of about 12 inches and inhabits shallow waters: inner and outer reef flats, back reef areas, coastal lagoons, barrier reefs, sandy and muddy areas, rubble-filled patches, and seagrass beds, where it feeds

Captive Care:

In general, sea cucumbers are gentle, unassuming creatures that mostly look like a shriveled-up old cucumber, hence the name. In the wild are many species of deep-sea-dwelling cucumbers, but those in the aquarium trade, including Holothuria edulis, come from shallow reef and coastal areas. Those from the shallows are known to be especially good sand sifters and are quite hardy, which is why they are collected. Sand is taken up by the tube feet surrounding the mouth, and through the process of digestion the algae and other microfauna on the sand is absorbed while the sand particles themselves are excreted.

Many of these creatures are nocturnal and all require large amounts of food. Since it is almost unheard of for an aquarium to have enough detritus to sustain a sea cucumber for any length of time, sinking algae pellets should be fed as a staple, with sinking shrimp pellets occasionally offered as a treat. These roaming sand and rubble cleaners should never be placed in newly established aquariums, as they will starve. Be forewarned, sea cucumbers will grow smaller and die if they don't find sufficient food.

If sea cucumbers are stressed and pestered by tankmates, they must be removed from the aquarium before they release the deadly toxins holothurin and holotoxin. Although these toxins are rarely released, they can result in quick deaths if they are. If a cucumber is sucked into a powerhead and shredded, an immediate major water change, increased protein skimming, and the addition of a canister filter with an ample amount of activated carbon quickly may help to save the tank, but there is no guarantee.

When selecting a new specimen, be sure the body is free of tears, cuts, sores, or oddly colored areas, as damaged specimens rarely regain their heath in closed systems. Due to its large size and correspondingly large appetite, H. edulis needs a large, open sand area that is free from obstructions so it can feed. Large and aggressive fish, such as some angelfishes and triggerfishes, do not make good tankmates.

Also keep in mind that cukes are very vulnerable to sudden changes in specific gravity or salinity, so acclimate one carefully by slipping the specimen out of the shipping bag into a separate acclimating container. Drip acclimate it carefully before netting the animal and transferring it to your aquarium. Do not allow the water in the acclimating container to enter the aquarium. 

Water Requirements: These animals are not fussy about water quality, yet the following recommendations are suggested: calcium 380 to 430 mg/l, alkalinity 2.5 to 3.0 meq/l, pH 8.1 to 8.2, specific gravity 1.024 to 1.026, and a temperature range of 74° to 83°F.

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