What is Causing Damage to My Acropora?

I noticed my acropora were extending their mesenterial filaments and then found this spot at the base which is receding. I noticed two aiptasia right next to this part that was receding, which I promptly dispatched to that great aquarium in the sky. Would aiptasia cause the acropora to recede like this? If so, how long should it take for the area to be covered again?

 

Probably low alk or alk swings.

Some acropora will display mesenterial filaments with simply cleaning the glass or adding any food to the tank, it's not a bad sign, but may be a sign of stress. Get your alk stable and feed the corals some food like ReefRoids, ReefChili, Rod's Food, Acropower, Spongepower......

 

Corailline, what should I be shooting for in terms of dkH? 8-11? Once the alk is stable, how often would I feed the acropora? Would I feed the other corals as well?

 

One step at a time. Fix alk then we can address anything else at a later date.

 

Got it. It's easy to get carried away. My dKH dropped while on was on vacation to dKH = 6. It's up to 8 now. Should I try to get it any higher than that?

 

I came in this morning and found the damage had progressed a little further and realized there was an almost completely transparent little tube progressing its way across the coral. Where the light hits the damaged part of the coral (dead center in the photo), you can just barely make out the outlines of this tube. I picked it off with a paperclip. It almost seemed like a sponge, which is becoming more prevalent on the rock in my tank. Is it possible for a sponge to eat a coral like that? Is this thing likely to grow back now that I've picked it off?

 

Nope never heard of that. Images always image man.

Sounds like newer tank growing pains. Even a tank moved needs to cycle to a lesser degree.

 

I removed the suspect before I could get a good photo. It's in a hard spot to photograph anyway. If it comes back, I'll be sure to photograph. Thanks for the help, per usual.

 

Oh, and I should mention that I received my Salifert magnesium kit today. It looks like my magnesium level is 1540 ppm. I will raise the dKH a bit more, but it's currently at 8-9. I've been dosing the alkalinity solution.

 

http://jus-tone.com/misc/reef/acro-1.jpgIt seems my acro is healing up, and I'm hyper-focused on the area that had been damaged. You can see the live coral slowly starting to fill in the missing area. However, I noticed part of the base of this coral is light and part of it is quite dark. Is this simply where the light and the shadows end up falling that cause a spot to be darker or lighter? I know the rock this coral is planted on recently moved, and I think most of that lighter area was in a shadow before.

Does that make sense or is it losing color in that area? The tips of the coral and everything else is a deep purple (except on the underside, of course, where you don't get much light). Perhaps I am getting paranoid . . .