What causes zoas to "dome" like this?
 

These People Eater zoas have looked fine for weeks but a few days ago one of them started to over-open (turning itself into a dome shape), and then the other one started doing the same thing yesterday. None of my other zoas are exhibiting the same behavior.

Does anyone else have experience with this kind of behavior?

Not sure why the pictures didn't upload. Possibly too large? Let's size them down a bit and try again...

Further info... It seems like they are unable (or unwilling) to close up completely. I gave them a quick CoralRX dip and they shrunk while being handled and dipped, they didn't close. It's almost like they are "cramped" in the open position.

They should go back on their own.

My experience is they dome when the light level is too high for them. Other zoas look fine.

i have same problem several months back too ..they lasted like this for ever..never went back to normal...then the melted away....thats just my experience...never new why...

Hmmm what have you been dosing? They say call a doctor if it lasts longer than 4 hours. :D

Sorry can't help, but wanted to subscribe to this thread for info and replies as I'm curious.

What is the name of the zoas in the OP?

I have the same ones. They domed like that and stretched their mouths open wide while reef roids was in the tank yesterday.

I have a colony that does the same thing and was going to ask as well. Not enough light?

I also have a colony doing that. It's been happening for a couple months at least. They're on the sand bed, but directly under a high power LED.

This was my thought. But it's just a thought. I haven't tried moving them or anything.

A have the exact same zoas....maybe a bit darker variety. Mine do the same thing...one or two heads 'dome' and the others are fine. The colony can't even agree on light levels.

Moved them to a less intense area and they stopped doing it. Now they are stretching and asking form more light... lol

Not as “domed” but what do you guys think? Down near the bottom and slightly shaded by a large leather coral about 12” above

The ones right above look fine. Dome comes from anything wrong. Light, salinity, etc. it’s just how they get sick

Sometimes having too clean of water can be an issue. Like really low phosphates.

Weird. I have a colony that has been growing like crazy for the last 2 years and now they started to dome and wither away. But I think mine was due to a spike in temperature. My tank reached 84 degrees and that's when the symptoms started.

When I have seen the dome appearance it was due to high level of light. If left alone in the same spot I have noticed them melt away. Trying moving to shaded area and see what happens.

mine did same thing ..melted away...i moved them around also didnt really help...maybe it some kind of disease..when they dome there doomed..lol...

No answers ?

Everyone answered. .

i have the same problem with mine too,out of 50 heads only like 5 are like that.i move them on sand bed see if they do any good.idk but the very top one is close but seems like a small head is popped out.http://i1262.photobucket.com/albums/...psjncwgp8y.jpg

Most likely too much light. Alot of people raise their zoas under super low light, some even use just blue u need to acclimate them to the new light.