Lights on too long?

So I get these sweet new T5 lights. 4 x 39 W, 2 - actnic, 2 - 10K White

I just timed the same as I had my junk old 6500K single bulb on, about 12 hrs. Well, the brown algae (and turning into hair algae) is going NUTS!!!

I'd almost think the tank was cycling again.... I hope my yellow Tang is ok, he's awesome. Anyway, if I reduce the length of time the lights are on, you think that would help fight this algae problem?

Its a 40 gallon bow front, I have the lights on thier legs so they are about 4-5" from the surface of the water, I removed my glass tops, and the total water depth is about 20"

Thanks guys! As always, the help and recommendations I get here are so super helpful! Keep it up!

-EDIT- Also, this room gets quite a bit of ambient sun light (none direct) from a West facing window.

 

I run my T-5 lights for 9.5 hours per day. So, you may want to shorten your cycle a little.

However, something has to be out of whack to get algae problems. What's your water's parameters? Calcium, magnesium, dKH, PH, Salinity, Ammonia, Nitrite, Nitrate, and Phosphate.

 

Dont have Calc, Mag, dKH tests (yet)

40 gallon tank,
80 degrees
0 nitrites
20 ppm nitrates
0 ammonia
1.024 salinity

 

If you keep corals, whenever getting new lights (or even new bulbs for an existing light) you always want to acclimate phase in the photoperiod or height from the tank. Some people raise their lights, use the same photoperiod, and slowly lower the lights over the course of a week or two. Others put the light in the final position but slowly ramp up the photoperiod over a week or two.

Example;

Day 1 5 hours
Day 2 5.5 hours
Day 3 6 hours
yada, yada, yada

 

Yea as Inwall said. It is likely an acclimation period. With more intense lighting you will see and increase of algae but it will be short lived.
Be careful with you feeding and perform normal water changes. Maybe pick up a few more snails and hermit crabs

J