How often to change UV light bulb?

[astro]

Any idea?
Can recommend a external canister filter with built-in UV?
Thanks

[astro]

Any1 know?

[Shadow]

is this for planted tank? you are not suppose to turn on UV light 24/7 on planted tank because it will oxidize the celated iron.

[astro]

No, it is not. Using it on my tank of silver dollars & silver arowana for many years 24/7. Dont know still effective onot

[Shadow]

NA uncle lust time told me that the uv set have those opening that will glow blue color. If no glow that mean need to change. However model to model might be different.

[astro]

Opening?? Let mi check