Lighting

[dsaundry]

With all the different types of lighting out there I have two questions. First of all I am currently running a 48" 250wmh with 4-65w pc. This is on a 72g bowfront reef set-up. Question number 1- how long should you keep the halides and the pc on during the day and is this set up ok for a 72g bowfront?
I am also going to be taking down my 90g freshwater tank and converting it to a marine predator tank. Question 2- My setup will be with a 48'pc and fiji-sand as substrate. Is a 48" pc adequate?
Happy Holidays