Sun Coral colonies not opening?

Eternal_ · Mar 5, 2024

Hello, I have a 29 gallon with a 10 gallon sump that is mainly for NPS corals. I do have some easy LPS and gorgonians in the tank as well but most of the corals are NPS sea fans and sun corals. I have had the smaller colony of yellow sun coral for around 2 months and a larger colony with yellow and orange mixed together for 4 days. I have unfortunately lost 2 heads on the smaller colony and since day one the polyps on both corals have looked extremely deformed. The polyps look like they are pinching right before the mouth and the polyps do not open all of the way. It is incredibly frustrating because I have been feeding it several times throughout the night and all of my other NPS gorgonians are all open and happy. Any assistance would be greatly appreciated.

Parameters:
Nitrate: 3ppm
Phosphate: 0.4ppm (It is high because of the powder food I am feeding the system)
Calcium: 420ppm
dKH: 9
Salinity: 1.025
Temp: 78.2 F

I use different foods throughout the day and feed the system 2-3 times.
Feeding:
Mysis Shrimp
Cyclops
Reef Plankton
Baby Brine Shrimp
Brine Shrimp
TDO Pellets (x-small and b2)
Fish Eggs

I also use AB+, MarineSnow, Reef Snow, ZooPlantos-S, Oyster feast, Phyto feast, and occasionally reef roids.

Lasse · Mar 9, 2024

My yellow that are placed in the light will not show any polyps before my evening feed. The ones sitting in caves have their polyps out for really all time. I have notice that they can, sometimes, be grumby and not show any polyps for a week or so. Newly introduced colonies can be "grumpy" for a month or so. It seems also that the do not like the proximity of a pump

I feed exclusive with frozen freshwater cyclops and frozen adult artemia

Sincerely Lasse

Acrohunter · Tuesday at 7:32 AM

I recently acquired a sun coral colony too and it is quickly becoming one of my fav coral in the tank !
From what i gathered, sun coral can take quite some time to be acclimated to a new tank. Give it some time because based on the picture, your sun corals looks fine.

For now, keep a close eye on it for a week to understand their behaviours. Most of the time they open up mainly when lights are out since they are nocturnal by default. When you see signs of them slowly opening up even the sllightest, prepare meaty food and target feed them lightly for the time being. Worry not, their tentacles are rather sticky and will catch on bits and pieces of the food you spot feed them. They are actually a very hardy coral and if you are consistently spot feeding them, they will grow over time.

For placement, consider putting them in a higher flow area to allow them to catch any food drifting past them. As for lights, it does not really matter but if you place them in a shaded area/cave. they would likely open up more often and sometimes even during the day. Good luck !