Mine are hairy in the daytime as long as I don't have them too close to the light. I have two frags, one down low away from the light and it looked great and another in the same tank up high on a frag rack that would not come out at all. I moved it down and it came out the next day. This applies to my bright green one.
I also have a teal hydno but it does great right under the light.
I have metal halides 20K so I have run into several things that won't put out polyps high up in the tank. But with two frags in the same tank it was pretty obvious that the high light was bothering the one.
Candy