"Why are my Zoanthids closed?" - Care, Pests, and Troubleshooting


Just found a couple of Nudibranches on my polyps and was searching for some help when I came across this write up. Really helpful and informative, thank you


Well-Known Member
Thanks for Bumping... I refer any member with zoa problems to this thread, the best write up I have ever read !!!


Thanks for this guide! I've been hunting craps for the big gold medal the last days, trying to find what tore down my zoids. 7 dead crabs later and still crappy zoids, i came over this post, and learned about Nudis. So i checked my zoids for nuids and they were INFESTED with them. Stange thing, when you know what to look for you find it, and vice versa.


New Member
Thanks for the info, one of my zoa colonies is starting to close up, and I panic and have been trying to get the water cleaner cleaner, (my local FS told my any nitrates/phosphates are bad bad bad) Will try feeding them some more food and see how they respond.


Well-Known Member

to ReefSanctuary, a real Sanctuary of reef forums, with lots of very nice members

Start a new tank thread & share your tank with us - we love pics :)


Princess Diana
Zoas are so pretty! Good info, this does need to be a "sticky" :)
Just bumping it up for other Zoa lovers :bump:

Edit: HEY, it's already a sticky ;)


Well-Known Member
Pretty sure I seen a similar post and someone posted a link to this thread yaya!
Good stuff n stuff.


New Member
Nice guide, very helpful.
But still, I would love to share one mine experience... When I moved from Europe to Tobago (Caribbean island) where I currently live, I was shocked when I visited one amazing beach. In fact it's a small bay with very shallow water (for the most part of the bay water is knee-deep or waist-deep)!
That shallow water is full of corals - all kind of corals, and, what is most fascinating for me - countless Zoanthid colonies! Like a carpet!
Why am I saying this?
The point is that some of them live in very small - few centimeters deep hols in the rocks on the beach! Unbelievably! In small hols on the strong Caribbean sun - can you imagine temperature in those hols? And they are wide open!
Also, they live everywhere in that shallow water....

Also I was curious and I tested water quality on that reef and on many other reefs around the island - and I was very surprised that many reefs don't have such a perfect water quality at all! Ammonia was present in some of them (especially in that shallow reef) - believe it or not! But still, everything is very alive!

My point is - people, maybe we pay too much attention to the water quality and all those things. Everywhere on the internet where i read about reef aquariums I read all the time about water chemistry... quality.... but even in the nature itself water is not perfect!

One more interesting thing - on all reefs here salinity is much higher. Usually specific gravity is around 1.030 or even higher!

It's lover on some beaches which are not near coral reefs....

Yeah, I took few Zoanthids from that shallow bay/reef an put them in the aquarium, and after few minutes they were wide open. And after few months they look very happy.
Only problem which I have is bluehead wrasse which (from the reason unknown to me) loves to swim above Zoanthids all the time and often he touches them, and they close! First I thought maybe he likes to swim in the water flow, but even when I moved Zoanthids he just suddenly changed his swimming route and there he is - above zoanthids again! I even think to get him out of the aquarium!