Here's a couple of rules I like to live by when starting a SW
unit ... Before anything.
1- skimmer......make it double the tank intake.
Everything else comes after
Because if your water ain't right from the beginning then your Screwed.
And the skimmer is the hart of your filtration.
Then everything else can fa in place,
Think good about the tank you want when it comes to size ... Long,tall,cube,big,small cause then you limit your self to the type of inhabitants that you can put in. Enjoy lol