Pictures?
I was thinking the same thing but I haven’t changed the light or flow and they used to be fine and growing.
I have 5 zoa frags that look about like that: extended, but not open. They were that way for about 3 weeks in QT and now a week in display. I dipped in H2O2, coral RX and bayer, no change. In QT, I tried different light and flow, no change. Strangely enough, they were open and looking great the first week in QT.
This is why @footgal is amazing@pseudorand is correct that zoas are only dead after they’ve completely melted (they will disappear completely and it’s not harmful to anything in your tank if this occurs unless it’s a very large number of zoas like 30+ at least). Tall stalks are definitely indicative of a lighting issue, and they should be given more light. The reason behind them failing to open could be a lack of iodine in the water. Are either of you dosing a trace element/iodine solution and what are your water change schedules? If you think this may be an issue, I’d pick up an iodine supplement (there are many available, choose one that works well for your tank’s size and your schedule) and do a water change, you should see them open within 5 days of those changes if iodine is the issue
Is it worth testing for iodine prior to dosing? A water change is certainly a good idea when things seem out of whack.@pseudorand is correct that zoas are only dead after they’ve completely melted (they will disappear completely and it’s not harmful to anything in your tank if this occurs unless it’s a very large number of zoas like 30+ at least). Tall stalks are definitely indicative of a lighting issue, and they should be given more light. The reason behind them failing to open could be a lack of iodine in the water. Are either of you dosing a trace element/iodine solution and what are your water change schedules? If you think this may be an issue, I’d pick up an iodine supplement (there are many available, choose one that works well for your tank’s size and your schedule) and do a water change, you should see them open within 5 days of those changes if iodine is the issue
It's very difficult to test for iodine. The best kit is Red Sea but even that is still wildly inaccurate because iodine must occur in such small amounts. The only real way to test for it is through ICP but often, that is too time-consuming and the zoas have already deteriorated beyond the point of saving them by the time a test comes back. Iodine in a reef tank is also essential for inverts like hermits, crabs, and shrimp to successfully molt so it's good to have some in there anyway.
It’s always good to get an ICP every 6 months or so, maybe once a year after you feel your tank is mature and stable. It just lets you know your kits are working, there’s no contaminants, and you’re doing good with trace elements. It’s mostly for peace of mind but it may also reveal something you never even thought about!
