ID?

I have tried a lot of different locations for these guys, but they never seem to open up much.  does anyone have any idea of what they are and the best place for them in my tank?

Alk=9.1, Ca= 425, NO3=0, PO4=.08.  I have two hydor 1150 at each end of the tank (90g long).  I thought that it might be xenia at first, too.  but when they do decide to open a little, the inside is bright green. 

Well I still won't rule out Xenia but if the centers are bright green then it's more likely Clove polyps. In either case they are sensitive to P04. I would run some GFO or Phosban to lower those Phosphates and see if that doesn't help solve the problem. They also don't need, or like, a ton of light. I see it's on the sand bed but what type of lighting and how many hours a day are the lights on?

blue sympodium?  Does anyone have experience with these?

Looks like Sympodium to me too. It's in the same family as Xenia but does not pulse. It does well in low to medium light and any flow. This coral is sensitive, not at all as hardy as Xenia. It's a good idea to know the conditions it came from. First try different spots on the sand with slow flow and lower light. As it slowly starts to respond, move it closer to where you want it. It's usually a very slow grower.

After 4 weeks if it's still not opening, at any time day or night, it's probably because it doesn't like the current tank environment. Like I said above, it's a sensitive coral that does not do well in half the tanks it goes into, even mature tanks. I'd consider trading it to someone and try again in 6 months. Maybe the way the tank changes in 6 months or a different Sympodium colony will like what the other didn't.

Aloha,

Mark 

Edited by Mark Peterson - March 29 2016 at 7:19pm