How often to change light fixture tubes?

[Bigzmey]

Do you guys follow manufactor's recommendations? Mine says effective for up to 10,000 hours. Or you change them once a year? I have a freshwater planted tank with 36" fixture with 2 T8 tubes.

 

[toddnbecka]

Regular output FL bulbs start losing their "mojo" after a year, but judge by the condition of your plants. I replace bulbs when they burn out, but I only grow Najas, hornwort, and surface floaters like Salvinia and duckweed.