Just been broadcast feeding Reef Frenzy 2x a day. Zooplankton & Phytoplankton 1x a week about 5ml each via the sump, right before return pump. That's it.
I've had this Acan for a year now, from just 1 head. It's been in that spot for a long time. My other Acan is fine about 5" from this one.
I find target feeding acans to greatly improve their health and growth. It doesn't seem like that is the issue here though. Any new fish or inverts that may be irritating it? Or changes in flow? Really though a coral closing up for 2 days is not something to get too concerned about.
What lighting are you using?
I had strictly leds over one tank of mine and always lost acans after 6 months to a yr. never figured it out. My other tank with same LEDs and additional t5s, acans would thrive. Parameters were very similar in both tanks also
Although it's not as swollen today, it still remains weird. I'm wonder if while messing around with my Gyre (switched sides for a minute) if it got hit with some not so gently flow, and I didn't notice at the time.
@guzzlo
-It's been under LED's for 10 months. Hopefully this isn't the case of its illness. No way can I add T5's.
If no tissue loss has happened I wouldn't worry to much. Flow can cause them to recede or if a fish decided to peck at it out of boredom or for whatever reason they will do this. How does it look with the lights off? If it appears the same in blackout I would dip it to ensure its not a parasite issue. Then watch and target feed it. Good luck