What is this?

[Irishman360]

This has been on my Zoas for quite a while now. I think it might be coraline would like another opinion on this. Am I able to get rid of it, is it harming the zoa, can I save the zoa?

1. Temp of tank - 80
2. Ammonia - 0, Nitrate - .2, Nitrite - 0 , Phosphate - 0, Alk - 9.5, PH - 8.2, Mag - 1760, Cal - 480. Water change was done less than 24hrs when tested I know Mag is high, change was 17%. Red Sea test kits.
3. Salinity 1.025
4. It is on a frag plug
5. Have you made any changes just prior to or during the issue? Added more corals but nothing around the zoas to infect it. New corals were dipped for 10 minutes as well, coraline was on zoas before addition.
6. Low flow. Using kessil lights that come on slowly then max light for about 4 hrs then down to 0.
7. Additives - None

 

[cloak]

If you talking about that purple spot then yes, it's just coralline algae. If the zoanthids are healthy they'll most likely grow over this given time.

 

[Irishman360]

If you talking about that purple spot then yes, it's just coralline algae. If the zoanthids are healthy they'll most likely grow over this given time.

Yes I am talking about the purple spot. They have been closed up for sometime now and only one pod opens up. Are they going down hill?

 

[cloak]

Yeah, not opening up for extended periods of time is not good. Being that your magnesium is pretty high, maybe this is having an adverse affect on the polyps. Do you know what kind they are? Sometimes Zoanthids will just decline for no apparent rhyme or reason though. Rastas, Blue Hornets, Purple Hornets, Gold Mauls have all done this to me. They look good for the first 10 days or so and then they just stop opening up and basically disappear.

 

[Irishman360]

Yeah, not opening up for extended periods of time is not good. Being that your magnesium is pretty high, maybe this is having an adverse affect on the polyps. Do you know what kind they are? Sometimes Zoanthids will just decline for no apparent rhyme or reason though. Rastas, Blue Hornets, Purple Hornets, Gold Mauls have all done this to me. They look good for the first 10 days or so and then they just stop opening up and basically disappear.

Only one or two heads will open up during the day the rest are pretty dormant. I moved them up higher in my tank so hopefully that will help.

 

[zoafarm]

+1...my bet is the high magnesium. I've seen similar effects when I was fighting bryopsis.