How to change bulbs

My pc bulbs are now a year old and I know I need to change them, but my question is, should I change them all at one time or should I do two at a time? if I do two at I time would I change both actinics, or 1 actinic and 1 of the 10,000k?

 

I would change them all.

 

How many reefers does it take to change a light bulb?

Do it all in one shot. I change mine every 6 months, I clean the fans and wipe down the reflectors around the MH's.

 

ive been told, you replace one at a time. not all at once. could be too much of a light shock to your corals. do one , then a week or so later, do another. just what ive been told, and will follow.

 

I have heard both ways, that is why I asked the question. I wanted to see what other people do. I really dont want to shock the inhabitants with too strong of light, but do pc lights really put out that much? The reason for my concern is I have a clam and some sps and lps high up in my tank. As of now they are thriving but I dont want to cause any issues.

 

I personally would play it safe and change a percentage of the bulbs every week or two.