How much light is too much light

[BillyPrefect]

There's a neat looking tank sitting at PetCetera..., however you spell that... it's 16L according to the box, supposed to measure 23X6X8 ... if you were to go say 2X36 from AH Supply that would be 72 W of CF light over er, 4 or so gallons... isn't that plenty? I'm asking people in the hopes that I don't spend $200 on something that can't support life. HELP.