Big Black Slug in my aquarium

December 3, 2007
From: Shelly Craigie

I found this slug in my reef tank yesterday. It's the first time I have seen it and I have 'lost' 2 fish recently. It has a grabby hand like thing on it's butt. It's black with a purple rim around it. It also has 2 horns. Do you know what it is?

Locality: Fish tank. Length: 2 inches long . Photographer: Shelly Craigie .

Shelly Craigie

Craigie, S., 2007 (Dec 3) Big Black Slug in my aquarium. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Shelly,

Although you didnt give me any indication where in the world your slug may have come from I am pretty sure this is Dendrodoris nigra which is found in the tropical Pacific and Indian Oceans.

The general shape of the animal, the arrangement of the gills [which you describe as the 'grabby hand like thing'], and the red band around the mantle are all characteristic of that species.

Have a  look at the species Fact Sheet for more information. The two 'horns' are its rhinophores - which are specialised tentacles used to smell its food. You mention losing 2 fish recently. Dont blame the nudibranch - or its 'grabby hand like thing' - this nusibranch only eats sponges.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Dec 3). Comment on Big Black Slug in my aquarium by Shelly Craigie. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Dendrodoris nigra

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