Replacing T5's timeline

I like to change them in stages...At the 12 month I start changing one bulb every week. On my ATI that takes me to the 14 month range...I have no proof of this but I believe it allows my corals to stay happy by not making a huge change in par and spectrum all at once.

 

I won't run mine any longer than 10 months. I have access to a PAR meter, and trust me, you don't want to run them longer than that. They can drop from where you were getting say 220 down to 160, the PAR will slowly drop and yes, your corals will acclimate, but they won't be as happy. i.e growth. The other thing to think about is waiting so long that when you change them, your corals are having to readjust to the correct higher PAR and intensity. I also like to change them in intervals. Write the date of when I started using them, and then replace each bulb bi monthly. By spacing this out every 60 days til you get them all replaced, it is much easier on the corals and the wallet.