What is eating the Halimeda?

[MusicTeach]

Not an emergent hitch-hiker question, but one that has had me interested for quite a while. Fortunately for me, my halimeda is growing faster than it's being eaten. See pictures below for examples of how it is being eaten.

It's the holes in the middle of the leaves that led me to believe something is actually eating it.
I've never seen anything eat it, so it's probably either really tiny or nocturnal, or maybe both! What do you think?

 

[TriggerFinger]

Do you have any snails? It almost looks like the marks caterpillars make on my cabbage plants

 

[Dancingmad]

For starters - what do you have in your tank?

I had a YT that would get after ALL the algae. Stuff he wasn't supposed to like to eat (such as Halimeda). Had a forest of shaving brushes (Really cool to watch those propagate - they send runners out under the sand and a new ones literally just pops up). Mr. YT decided they were tasty and mowed them all down.

 

[S-t-r-e-t-c-h]

I'm guessing an urchin, but I'd love to see a list of what's in the tank...

 

[Nick tang]

My sea urchin ate all my halimeda.

 

[MusicTeach]

For starters - what do you have in your tank?

I had a YT that would get after ALL the algae. Stuff he wasn't supposed to like to eat (such as Halimeda). Had a forest of shaving brushes (Really cool to watch those propagate - they send runners out under the sand and a new ones literally just pops up). Mr. YT decided they were tasty and mowed them all down.

Well, that's the question I got live rock from TBS, and it had all sorts of critters on it. Most of which I probably don't even know about. But, let me tell you about what I purchased beyond the original rock.

Fish: 2 pink skunk clownfish, 1 midas blenny, 1 red firefish, 1 purple firefish, 1 citron goby, 1 mandarin dragonet
Inverts: 2 cleaner shrimp, 2 emerald crabs, 2 hermit crabs (red legs?), 1 pistol shrimp

The rock also came with whelks (removed), gorilla crabs (removed), cirolanid isopods (removed), 25 urchins (all removed - haven't seen one in 6 months), bobbit worms (in process of being removed), keyhole limpets, 1 hermit crab (additional), 1 pistol shrimp (additional), and lots of worms and pods, including spaghetti worms. One spaghetti worm lives right underneath the halimeda stack.

So, I don't think it's urchins, being that I've pulled out so many, and haven't seen any in 6 months. The cleaner shrimp migrate to that side of the tank every night... but would they be eating halimeda? Maybe the hermit crabs? But I agree with TriggerFinger - looks like caterpillar marks.

Hope this helps - and thank you all again for offering your thoughts and insights!

 

[TriggerFinger]

25 urchins?! I had one dime sized hitchhiker that didn’t make it...Were they all small?

I have no idea. Maybe some type of snail that comes out at night only? Has to be a caterpillar.

Edit: a quick google search shows a couple responses of parrotfish and urchins. A lot more “nothing eats this” answers though.

 

[MusicTeach]

Yeah, that's what I figured, but I don't believe I have either.

Yeah, it started and I saw two little urchins and I thought they were super cute. And then they grew up. And 23 others literally crawled out of the rock. Medium length spines, dark purple. And two tuxedo urchins too.