Yikes, okay. Thanks for the info. Time to Google more!
Need to decide this or a pH controller... well not need, just nice to have things!
In my experience, you really don't need to own a PAR meter.
Maybe it would be more useful if I was constantly setting up new tanks with different types of lighting, or if I wanted to mess with my bulbs a bunch, but for the most part you test your PAR once or twice and then the thing just sits around in a drawer.
Makes a lot more sense to try and "rent" one. Whether from your LFS or another hobbyist, or buying it, using it, then returning it
Owning a pH controller is a solid investment.