BL1
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You should go fo the biggest size tank that you can fit in your stand. With refugiums the bigger the better
You should look at the octopus skimmers, they are highly recommended. I'll be picking one of those up in a few months when I upgrade mine. And for the heater, I think you'd be better off getting two smaller one instead of the one large heater. That way if there's a malfunction on one you have the other as a back up
+1 Reeffreak This is the Skimmer I use:
Super Reef Octopus Cone Skimmer XP-2000SSS
It does an excellent job.