I just went through the same thing with my curve 7. Took around a month to fully break in. Part of it may have had to do with it being in a new tank with relatively low nutrients. I have it in 10 inches of water. The only way I could get it to start getting some dark skimmate was to run it at the max setting for 24 hours, then turn it to between max and 3. Wait another 24 hours turn it to 3, 24 hours, turn it to between 3 and 2..and so on until it starts producing skimmate. When it gets to the point of producing skimmate dont touch it..just let it run. It may stop producing skimmate here and there while it is breaking in but just let it go after you see skimmate. Mine is working really well producing very dark skimmate with it set between 2 and 1. It does skim a little dry, but it is really dark, almost black. I have it on a 150 with 30 sump, and feel it is more than enough to keep up with a medium bioload.
