Skimmer Strength for 120g?

Hello,

I am in the planning stages of my 120g 48x24x24 tank.

I have a nano tank, with no sump, so I'm new to the need for a skimmer. Is there a certain strength or turnover required for 120g tank? What is the "Standard" I dont know if it matters, but Im looking to make this a Softies tank.

Any help would be appreciated.