I'd be inclined to try the stock one out first, since there's little resale value in proprietary skimmers. You may find it's sufficient. I don't think you'll be able to fit the IceCap in the same location; you may have to place it in the pump chamber.
Did you wind up trying out the ice cap? I'm running this tank without a skimmer right now but my phosphates are pretty high so wanting to pick one up. I tried the Aquatop one and couldn't get it to fill the cup so wound up returning it. Looking for other options.
On the note of skimmers, I have the aquatop recife 24 which has what looks to be the same stock skimmer. The skimmer location is a 3in square which makes it nearly impossible to fit anything in there. I have an Icecap K1 Neo (smaller than the nano) coming today in the mail and I'll try and remember to post here if it fits.
How is that ice cap working out ? Having same issues finding a skimmer upgrade … I got the Aquatop 40 .. thjnk that ice cap is a bit under sized .. says rated 5-10 gallons .. how’s it working for ya ?