ID of Unknown Microfauna

[sculpin2]

Howdy,

I have no idea what these are. They came in on LFS frags and came off during dipping. They are 1-3 mm in size, shaped like a flatworm, move VERY quickly (amphipod/isopod speed), have some type of legs and antenna, and did not appear to be associated with any fish in the tank. The frags showed no sign of coral tissue damage. I am assuming a type of isopod but am unsure.

Here's links to videos of them swimming I posted to Imgur:
https://imgur.com/qXnqPHU
https://imgur.com/ZjXiZdb (scroll to bottom of video)

Here's some images (sorry, they're huge):

Thanks!

 

[ramseynb]

Looks like isopods to me.

 

[sculpin2]

Probably, but what type? And is it a coral eater?

 

[mcgyvr]

Sphaeromatid Isopod (Sand Skater)
Harmless/beneficial algae grazer..

 

[sculpin2]

Thanks, man. Searching for that got me to Lionfishlair.com where they identify these as Serolid isopods rather than Sphaeromatid. Their Serolid sample is identical to mine.

 

[mcgyvr]

Thanks, man. Searching for that got me to Lionfishlair.com where they identify these as Serolid isopods rather than Sphaeromatid. Their Serolid sample is identical to mine.

I saw that and believe that the Serolid name ID there is just a mistake.
In a post on another reef board that I cannot name lionfish used the sphaeromatid name instead.
And Ron Shimek also came to the sphaeromatid identification..

One could be a suborder or whatever of the other.. Been so long since I learned that kingdom/genus/family/suborder stuff..

 

[Sugar Magnolia]

Those aren't sphaeromatid isopods. These are https://www.google.com/search?q=sph...ved=0ahUKEwip_qmqxt_ZAhWIjlkKHSNBCs0Q_AUIESgB

They are quite big and often confused with cirolanid isopods.

 

[mcgyvr]

Those aren't sphaeromatid isopods. These are https://www.google.com/search?q=sph...ved=0ahUKEwip_qmqxt_ZAhWIjlkKHSNBCs0Q_AUIESgB

They are quite big and often confused with cirolanid isopods.

I've found conflicting information all over the place as far as the identification of this specific critter..
and just don't have the time to dig deeper..

One site said that if you poke at them and they roll up they are harmless.. if they don't get them out..

Its a harmless isopod from what I've been able to find so far.

 

[sculpin2]

They roll up. You can see it in the video I posted. And they look like tiny versions of this grouchy guy:

http://www.oikonos.org/apfieldguide/album/Arthropoda/Isopoda/Serolidae/slides/UID%20serolid%20isopod%20002.html