Okay I have a different kind of lighting question. I'm a noob when it comes to aquariums but I just acquired a 90 gal
tank with a coralife 2 x 150 HQI MH
. The bulbs still work perfically fine but i was told that the bulbs are almost 3 years old and they NEED to be changed.
Why? What do new bulbs do the old working bulbs don't?