Hydroid or Nudi?

[trondsbr]

I am unable to ID this critter, although nudibranch and hydroid have come to mind. Was crawling up the glass about 1 inch from the substrate and actively moved the tentacles back and forth in a sweeping motion as if looking for food.
Length is 0.5 cm

 

[mscarpena]

Looks to be a filter feeding nudibranch. Will probably stave, but other than that should be harmless.

 

[LeslieH]

Neither. It's a teeny-weeny baby sea cucumber. We can clearly see the tube feet and the extended feeding tentacles. It wants good flow with particulates that it can pick out of the water & eat. Under low flow conditions it will either start moving to a better spot or brushing the tentacles over the substrate & glass to pick up food.

 

[trondsbr]

Interesting, would it have been a hitch hiker with a recently purchased coral and not the live rock since the live rock is over a year old to my system? I did some research and there doesn't seem to be an issue of cucumbers being pests to any coral so I will allow it to stay. Thanks for the information.

 

[650-IS350]

i was gonna say baby sea apple of sorts. filter feeder

 

[LeslieH]

All holothuroids are filter feeders or deposit feeders. A few of them have extremely toxic defense chemicals which may be released if they die or are stressed (sea apples are one of the these species). I think this one is among the more harmless ones. It certainly could have come in attached to a coral's substrate or even be a juvenile from an individual hidden away in the old live rock.