My Favia only seems to extend its tentecales when all of the lights are off, including the moonlights.  So this morning I got up turned off everything waited for a little while then spot fed him also. 

I talked to Eric Borneman about acans about 18 months ago. All of mine were developing pink skeletons and starting to die.

I learned two critical things at that point.

1) Watch your Magnesium with acans. They love it! Mine had dropped below 900 and was the cause of my problems.

2) Acans eat a TON in the wild.

Eric was telling me that they eat constantly in wild and suggested we give the same treatment in our tanks. Therefore I spot fed mine 2-3 times a week. It does get tiresome but my growth exploded at that point!

I thought it might be the raised magnesium but tested that out by not feeding for a couple months. Sure enough, growth slowed down. When I started feeding again, growth probably doubled.

I had a little 4 head colony turn into about 15 within a month.