What critters eat zoanthids?

kdx7214

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I've got one small colony of zoanthids in my tank. It's done okay, not really grown much over the past year, but stayed consistent. Suddenly it's started losing polyps. They are definitely being eaten as I can see the base has been scraped clean off the rock. What critters can do this?

What I have in the tank (that I know of):
  • Emerald mithrax crabs (2)
  • Hermit crabs
  • Peppermint shrimp (not seen in a year or more)
  • Numerous types of snails from a cleanup crew
  • Lawnmower blenny
  • Firefish goby
  • Unknown type of sandsifting goby or blenny
  • Unknown type of goby or blenny
There have been no new additions to the tank in the past year. I have had a problem with my tank parameters but am in the process of getting that back in order. The only recent changes are a thorough cleaning and the addition of kalkwasser to the ATO.
 

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Can you remove the rock with the zoa's and dip it to remove any potential pests. Could potentially be zoa eating nudis or spiders. Emerald crabs can also eat zoa's as they are opportunistic feeders
 

mfinn

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I've seen emerald crabs eat zoanthids. Some say they are just scraping off the zoanthids to get a better shot at any algae around them. But in my case I didn't see any of the missing zoanthids floating around anywhere.
 

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Could be the peppermint shrimp or emerald crab. Also agree that it could be zoanthid-eating sea spiders or nudibranchs. Spiders would emerge at night, so check a few hours after sunset with a flashlight, if you dip it then there's a good chance that (if it's spiders) they won't come off but if it's nudibranchs they will come off. Again, check at night as that's when they are usually active.

Emerald crabs and peppermint are known to snack on coral (sometimes) so watch for that


Edit: I only say it could be spiders as i just have cleared my system of them (I had leptastrea eating spiders) they would look like this
20231117_195915.jpg

They are very small so you need a keen eye to spot them
 
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kdx7214

kdx7214

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Can you remove the rock with the zoa's and dip it to remove any potential pests. Could potentially be zoa eating nudis or spiders. Emerald crabs can also eat zoa's as they are opportunistic feeders

I've already done that with Coral RX just to be on the safe side. I'm strongly suspecting there is an emerald mithrax still in there somewhere, even though I don't see it.
 
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I've seen emerald crabs eat zoanthids. Some say they are just scraping off the zoanthids to get a better shot at any algae around them. But in my case I didn't see any of the missing zoanthids floating around anywhere.

That's what I'm leaning towards. I don't see the emerald crabs at all, but they were in there at one point.
 
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kdx7214

kdx7214

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Could be the peppermint shrimp or emerald crab. Also agree that it could be zoanthid-eating sea spiders or nudibranchs. Spiders would emerge at night, so check a few hours after sunset with a flashlight, if you dip it then there's a good chance that (if it's spiders) they won't come off but if it's nudibranchs they will come off. Again, check at night as that's when they are usually active.

Emerald crabs and peppermint are known to snack on coral (sometimes) so watch for that


Edit: I only say it could be spiders as i just have cleared my system of them (I had leptastrea eating spiders) they would look like this
20231117_195915.jpg

They are very small so you need a keen eye to spot them

Well, I'd already removed the rock and dipped it in Coral RX, so I doubt it's spiders, although I guess it's possible. I did look after lights out with a red light but was unable to spot anything.

I think the peppermint shrimp is long since deceased. I've not seen it in months and at one time did have a six line wrasse (it died due to being egg bound). I think it's probably the mithrax crabs though, now that I've read more about them. I was hoping for them to control the valonia, but it seems they eat a bit more than that.
 

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Well, I'd already removed the rock and dipped it in Coral RX, so I doubt it's spiders, although I guess it's possible. I did look after lights out with a red light but was unable to spot anything.

I think the peppermint shrimp is long since deceased. I've not seen it in months and at one time did have a six line wrasse (it died due to being egg bound). I think it's probably the mithrax crabs though, now that I've read more about them. I was hoping for them to control the valonia, but it seems they eat a bit more than that.
I'd take them out, see if it stops. If it dosent then my best bet is spiders, they made it through an iodine dip and a freshwater dip, they're a pain to deal with.
 

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I've got one small colony of zoanthids in my tank. It's done okay, not really grown much over the past year, but stayed consistent. Suddenly it's started losing polyps. They are definitely being eaten as I can see the base has been scraped clean off the rock. What critters can do this?
I think the main clue is you don't even see nubs left. Just clean rock where they once were.
With sea spiders and zoanthid eating nudibranchs, they don't clean off entire polyps over night.
You usually see half of the polyp or nubs left over.
My bet is something with claws that scrape.
 

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