48-60" because the fixture is 48" long (arms go out the other 12") - will have the light all the way to the edges of the tank.
I got a 36 to 48" (light fixture is 36" - arms go out the extra 12") one to try out and it is going to the daughters tank which is 36" wide. Not enough light for a 48" tank.
Current USA Satellite Freshwater LED
Plus Light has an awesome remote and does all kinds lighting types like sunny cloudy lightning plus customizable options.
There is a couple of options for Finnex depending on how much light you might need, Fuge Ray and Ray 2 higher light. I haven't tried that one.