If you are looking for an in sump skimmer, I would definitely buy an Octopus skimmer. You will not beat it for the price and it will skim circles around any coralife model. I paid $180 for mine the (NW-200 on sale now, Google: OctopusSkimmer or ASMSkimmer) and it has an 8' diameter and is 24' tall. That is only 1/2 an inch smaller in diameter than the ASM G4 and yet it is only a little more than half the price of a G4. Also these skimmer are made from cell cast acrylic something the likes of deltec, euroreef, BM, BK can claim. Not the cheap extruded PVC you see with ASM, coralife, or red sea.
Here are a couple of pictures of mine in action. The collection cup was just emptied 2 days ago and this is only on a 55g
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HTH