Top off water shouldn't have any effect. I have one of these on my small tank and love it. It did take much longer to "break in' than any skimmer I've ever had. I don't remember exactly, but it was a few weeks, at least. If this doesn't resolve itself soon, I'd call Aqua-C tech support; they are excellent. Getting back on my soap box: IMO, company tech support is a great resource that we don't use enough. if a company doesn't have good tech help; I don't buy their stuff. BTW, Remora skimmers need very clean riser tubes to work well, even daily cleaning isn't over-kill. Also, if this is a new tank, there may just not be enough gunk to skim yet.