Unhappy Zoa's

DHouse · Mar 24, 2025

My mixed reef tank has been up and running for more than two years and I never really had any problems with it besides the normal problems associated with a mixed reef tank. Recently, some of my zoa's started closing up and a few melted away. Blue Hornets, Purple Hearts, Candy Apple's, and seveal others but not all of my zoa's are closing. Lazy Lashes, AOI's, Halle Berry's, butt Monkey's and several others are still opening up fully. None of my others corals in my tank are affected. Hammers, Frogspawns, St Thomas Mushrooms, Lobo's, etc are doing fine. I do weekly water changes with RO/DI water with TDS readings at zero. Tank temp is 79 degrees and salinity is 1.026. My parameters are pH-8.3, Alk-9.2, Calcium-425, Magnesium-1322, Phosphates-.05 and Nitrates-17.3. I've checked several of the zoa's to see if there were any flat worms or anything else but I could not see anything. The zoas, that are closing are not in one general spot. They are spread throughout the tank. The tank has good flow all around. I run carbon and GFO in separate reactors and have always run these. I have not added any new fish and the last time any corals were added was about 6 weeks ago. My question is, has this happened to anyone else and if so, what did you do to stop the bleeding. I used to love looking at my coral but now I'm just frustrated that I think that I'm doing everything right but that just isn't good enough.

BristleWormHater · Mar 24, 2025

First thought is a trace element issue, they need good levels of iodine and potassium.
@Randy Holmes-Farley

Tahoe61 · Mar 24, 2025

Are you dosing, and if so what?
How are you maintaining chemistry?
Are you actively looking at night for all Zoanthid pest?
Has lighting changed?

DHouse · Mar 24, 2025

BristleWormHater said:
First thought is a trace element issue, they need good levels of iodine and potassium.
@Randy Holmes-Farley

I dose twice a week with with Trace Elements

DHouse · Mar 24, 2025

Tahoe61 said:
Are you dosing, and if so what?
How are you maintaining chemistry?
Are you actively looking at night for all Zoanthid pest?
Has lighting changed?

Thanks for the response. I dose Sodium Bicarbonate every morning and trace elements twice a week. I dose calcium and magnesium when needed and do water changes weekly. I change my carbon reactor usually every other week and I change my GFO if the phosphates start to climb. I test weekly and all my parameters are tested using the Hanna Marine Master Multiparameter Photometer. I do look for pests that are not supposed to be in the tank nightly and lighting has not changed in the past year. My lighting is 2 Aqua Illumination Hydra 32's. Some of these zoas have been in this tank for 10-12 months and then all of a sudden they stopped opening. The ones that I could get of off the frag racks, I dipped in ReVive and put them back in and still no change. I have other corals in the tank that have not been affected including Hammers, Frogspawn, Blastos, Mushrooms, Nephthea, Lobo's, and Candy Cane. I don't burn candles, or use incense and nothing is sprayed in the air. My other reef tank has zoa's as well and they are all fine. Both tanks are in the same room. Counting the zoa's that are closed, there are at least 14 of them.