Nudibranch I.D.

August 20, 1999
From: Adam Walbridge

I have recently set up a salt water aquarium in my home, I decided to use live rock from Fiji. About a month has passed and several Tube Worms, sponges, and other growth has sprouted up. One morning I noticed a sluglike creature crawling out of the rock. I have exhausted all my resources locally in identifing the species. It is approximately one inch long, all black, and a small fanlike tail. It doesn't appear to have any stripes or spots, and is very smooth. Any assistance would be greatly appreciated in identifying it, so as to know whether it will harm any other organisms in the system.

Thank You
Adam Walbridge

Walbridge, A., 1999 (Aug 20) Nudibranch I.D.. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Adam,
I'm afraid you are not giving me many clues. The fanlike tail could be the gills of a dorid nudibranch, but have a look at the photo of Ceratosoma amoena to see where dorid nudibranch gills are situated, and what they look like. Failing that, the tail could be the feeding tentacles of a Sea Cucumber or even a fan worm. Sometimes fanworms can leave their tubes .... but that would be fairly risky business if you have fish in your tank. If it is an inch long you should be able to see if it has head tentacles or rhinophores which would pretty much confirm it is a dorid nudibranch. Another thing to look for is whether it has a foot. Sea cucumbers are essentially cylindrical and move by small tubular 'feet' much like a starfish.

If it is a dorid nudibranch it probably came with the rock as a recently settled larva on one of the sponge colonies which you say is now flourishing. Whatever it is, it is unlikely to cause harm, other than to eat a bit of one of the sponge colonies. Since 'live rock' is always a bit of a lottery I think you should give the beast a bit of a chance too. It has survived a fairly perilous few weeks being transported to your tank. Apart from natural curiosity in knowing what it will become, I think it deserves a second chance to prove itself.

Let us know if you succeed in confirming what it is. If a nudibranch, perhaps we can identify it for you. One possibility would be either Dendrodoris fumata or Dendrodoris nigra, both of which can be black.

Bill Rudman.

Rudman, W.B., 1999 (Aug 20). Comment on Nudibranch I.D. by Adam Walbridge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Is It Possible To legally Purchase Phyllidia ocellata?
    From: Jason Brooks, May 5, 2010
  2. Unknown sea slug
    From: Jupiter dale, March 19, 2010
  3. Re: Chromodoris annae in aquarium
    From: R. Grooters & M. Snoek, March 7, 2008
  4. Chromodoris annae in aquarium
    From: Mattias Westermark, March 5, 2008
  5. Hypselodoris bullocki and aquarium shops
    From: joshua sampson, November 21, 2004
  6. Concerning 'angelfood'
    From: Alan Osborne, March 19, 2004
  7. Hypselodoris bullocki in aquaria
    From: Steve Jen, March 19, 2004
  8. Hypselodoris picta in aquaria
    From: Susanne, March 18, 2004
  9. Question of an outsider ...
    From: Shoei, October 11, 2003
  10. More aquarium shop misinformation
    From: David Clay, March 23, 2003
  11. Need some advice - uninvited aquarium guests
    From: Jenifer, December 30, 2002
  12. Red Seaweed for sale
    From: Jim DeMattia, June 8, 2002
  13. Elysia crispata and Green Carpet Anemones
    From: Andy Feifarek, May 21, 2002
  14. Identity of Nudibranch mimic
    From: Raymond Mears , March 23, 2002
  15. Observing sea slugs in aquaria
    From: Sarah Bredensteiner, March 14, 2002
  16. We want to buy a nudibranch
    From: jennifer, March 10, 2002
  17. Opisthobranchs in Captivity - new book news
    From: Dave Behrens, February 7, 2002
  18. Introducing a sea slug
    From: Alisa Taylor, November 12, 2001
  19. More misinformation from nudibranch suppliers
    From: Michael Bloss, July 2, 2001
  20. Keeping nudibranchs in tanks
    From: Melinda Newton, May 31, 2001
  21. Keeping sea slugs in captivity
    From: Lorena Schwarz, May 28, 2001
  22. Sacoglossan Defenses
    From: Tina Calle, March 22, 2001
  23. keeping Spanish Dancers in aquaria
    From: Kyle, February 8, 2001
  24. Colored sea slug
    From: Robin, January 7, 2001
  25. Alternative to Sponges for Hypselodoris bullocki
    From: John Leventis, October 26, 2000
  26. Re: What do they eat?
    From: Darla Hatton, August 7, 2000
  27. Re: What do they eat?
    From: Darla Hatton, August 2, 2000
  28. Help identify species & what do they eat?
    From: Darla Hatton, August 1, 2000
  29. Re: what do they eat?
    From: Darla Hatton, August 1, 2000
  30. Sea Slug Info
    From: Cherish, April 7, 2000
  31. Seaslugs as pets
    From: Steven Grant, March 29, 2000
  32. Sea Slugs in a local Mall pet store
    From: Mike Thomas, February 13, 2000
  33. Advice on keeping nudibranchs in aquariums
    From: Phanor Montoya, August 22, 1999
  34. Can you recommend good aquarium species?
    From: Eirik Eilertsen , July 29, 1999
  35. Nudibranchs in the Reef Aquarium
    From: Theresa Coulter, May 23, 1999
  36. Re: keeping nudibranchs in the aquarium?
    From: Rob See, January 7, 1999
  37. Sea Slugs as Pets?
    From: Sam Noe, August 10, 1998
  38. Keeping sea slugs in captivity
    From: Stephen (Max) Gillies, July 9, 1998

Show factsheet and all related messages