Replacing bulbs

[NastyZ]

How fast should I change out my bulbs there about a yr old and I negletied to notice how old they were till this weekend I have a 8 bulb t5 should I change two bulbs per week 3, 4 or all don't want to shock my corals and raise the fixture isn't an option

 

[jdraider75]

I change out 2 every 4 days. I also have an 8 bulb. If possible raise light a few inches also and lower a few weeks after all changed out.

 

[NastyZ]

The fixture is as high as it can go but yea I think 4/7 days is good I just don't want to bleach my corals iv done that before not fun