New lights quick question

[DcoarM]

So my bulbs are almost 11 months old now, so went ahead and bought two yesterday and plan to buy two more in a couple of weeks. I bought two ATI coral plus bulbs. Would it be okay if I replaced both of them at the same time, or do I need to add one and then wait a week and add the second? The other bulbs on the tank are two ATI blue plus.

 

[ebushrow]

How many bulbs does the fixture hold? 4? I might change them each week if there are only 4 to be on the safe side.

 

[Reefing Madness]

You can change em at the same time. Wont' harm anything