I got this used and figured I'd use it as long as the bulb lasted and then replace plexiglass and put in LED strips.  In fact, I never used it as it's really too bright for a standard 10gal unless you are growing coral or such as this light seems to be meant for.  It is one unit that is actually two florescent bulbs, one very blue and the other cold white. I can't say how many hours on the bulb, but it's bright and unblackened. The black paint is starting to come off the aluminum on the bottom, but could be repainted. The plexi has a piece missing (see pics), but only the sealed end of the bulb is exposed there.