How long do I leave my HH and Atanic`s on?

I keep mine on for 6 hrs been doing that for about 3 years works good for me

 

I keep them on 10 hours.

 

Actually 6 hours of strong light is optimal for corals. Anything longer actually can do damage that that coral has to repair before it can start growing again the next day. Its called light saturation.
Lots of variables are involved though including par, depth, color of lighting and so on.  I would get the club par meter & check your levels.
Antinics are another story. You can leave them on for as long as you want. They are more for our benefit of viewing then the corals.
Whatever you do, change your times very slowly and gradually, or you may wipe out all the corals in your tank. Think of going to a tanning booth every day for 15 minutes, and then decide you are going to jump to 45 minutes.
You asked how do you tell?  How does your tank look?  Good colors, nice tips?  No algae.  If so, dont mess with it if it isnt broken.

 

xroads......only six hours? damn. I'm wasting a lot of electricity.

I'm running 16 t-5's over a 8' x 2' x 2' tank. 8 bulbs per side. 4 bulbs per ballast. 4 ballasts.

When I run my 'blue' lights there are two ballasts on driving 8 bulbs.

Do you think I should reduce my light cycle?

How many hours per day should I run my blue lights.

Damn I am confused all of a sudden....

 

Your antinic lights doesnt do anything for the coral, again, it is for our viewing pleasure since it makes the corals flourence.

Again it depends on par, and the coral. Some takes longer to reach that saturation point.

Your fish do need the longer days however.

If it is working, go with it. If you want, dial it back by 30 minutes and see if it looks even better. I have seen coral studies where coral growth actually accelerates when people cut back from 10 hours of intense lighting a day. The bluer the light, the less intense it is, so the saturation point will take much longer to reach.

 

When we set up our 120g and switched to 400w MH I set them on a timer to cycle on and off during a 8 hr period. I think they are on maybe 5-6 hrs max. The actinics are on when the MH's are off. The plan was to "break everything in" to the 400w, which are not on more than 1 hr at a time. That was last October, our tank has never looked better, no algae, and the coral growth is amazing. Im not changing anything.....