15-05-2022, 18:01


Glossodoris reddish-colored, white-toothed sea slug, caramel holodermen or caramel holodermen are found in the tropical waters of the Indo-Pacific region in such far-flung places as Tanzania in Africa and Mayotte in the Indian Ocean. From Sri Lanka to Polynesia, the caramel holodermen are considered a relatively common species. They are abundant in Hawaii, but less common and rarely seen in the Marshall Islands.

Glossodoris rufomarginata are mostly found on sheltered reefs, among rocky areas, and in open shady areas. They are active during daylight hours, but avoid bright sunlight and prefer shaded areas.

In the Marshall Islands, caramel holodermen often visit caves and ledges on the windward side of the reef and the spur system, where they feed on dark gray slimy sponges of the Thorectidae family. For most of the year, this area (where the sea-facing slope meets the tidal reef) is relentlessly pounded by strong waves and strong surges of water. The strong blows often dislodge or tear off chunks of sponge when it gets too big, and wash it across the littoral reef onto the sandy slopes of the lagoon. In the Marshall Islands, Glossodoris rufomarginata grows to almost 5 cm in length.


Unfortunately, sponges of the family Thorectidae, which are the only prey of the caramel holodermal clam, do not normally inhabit the area. Once the sponge is completely eaten and Glossodoris reddish can't find another sponge colony thrown ashore to feed on, the holodermal clam may starve to death.

The caramel holodermid clam is light brown in color, with the surface of its back and foot densely dotted with a layer of tiny red or orange-brown dots. The well-developed corrugated edge of the mantle has a broad white band with a red to orange-brown outer border, and the foot has a white outer edge. The retractable gill plumage and rhinophores are red to orange-brown with a white midline on the rhinophores and a white tint on the gill axis. There are yellow, white, brown, and red color forms of the clam.

The caramel holodermen is one of the most common species found in Hawaii. Specimens here grow to a maximum length of about 2 cm and inhabit relatively shallow reefs where their only food source, a dark gray sponge named Cacospongia.

Because of their special food habits, the caramel holodermen have a relatively short lifespan in an aquarium environment. They are insatiable sponge eaters, and are best kept in a well-established reef aquarium of at least 250 liters with lots of live rock, sandy substrate and lots of sponge algae typical of the area from which they were collected.

The white-toothed sea slug needs quite a lot of water movement, so an aquarium pump is recommended in a reef system. Like most invertebrates, this mollusk is very sensitive to water quality and requires stable water parameters.

Water parameters: temperature 22-26° C, hardness dH 8-12°, pH 8,1-8,4, salinity 1.023-1.025.


They are particularly sensitive to higher levels of nitrates and are completely intolerant of copper impurities in the water. Once purchased, clams should be acclimatized slowly with the lights off or in low light when introduced to a new reef system.

A large number of live sponges of the Thorectidae family must be present in the aquarium for normal clam growth. Without a constant supply of live sponges in their diet, Glossodoris reddish will starve, eventually acquiring a miserable appearance.



Glossodoris rufomarginata breeds constantly in established reef aquariums.

Glossodoris rufomarginata is sometimes available to tropical fish lovers in specialty stores and online from a variety of sources.



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