I bought a fluourescent light assembly on Ebay with plans on using it on my 10gal tank as a grow light (when 10g isn't being used for breeding). I received it today, and measured for what size bulb I need. It measures 17" between the mounting tabs. I can't find 17" lighting anywhere though. 18" is the only size close that I can find. I even looked at some lighting supply websites, and they're also 18". Are Fluorescent bulbs measured differently, for example from the end of each metal tip? Help.
