A couple of planning questions for 75g reef

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1. I want a sump with as much space for refugium as possible. An in-sump skimmer must take up a lot of sump room, I have seen some skimmers that are in-sump but can be plumbed to run out of the sump freeing up sump space (considering a Euro-Reef skimmer). Is there any downside to having the skimmer plumbed outside of the sump?

2. I may want to run FOWLR for 6 to 12 months before going reef. I will have 3 x 40W fluorescent fixtures available (two come with tank, one I have lying around). Is this enough to get decent coralline growth in a FOWLR?

3. For eliminating air bubbles in the sump from the skimmer, is there another option besides baffle walls? I have read about people running the skimmer output through a micron filter bag, does this make sense?