I use a BM Curve D9. I've heard people say they've had difficulty tuning them in. That wasn't my experience at all. That said, this skimmer has a DC pump and is probably more versatile than the AC versions. I get a very steady amount of skimmate so the design must be solid.
I have had a Curve 7 for about a year and a half. So far it’s worked well for me. Couple of things I’ve learned. First, water depth matters. I forget what Bubble Magus suggests but keep it within that range. Second, when you adjust the air mix I always give it a few hours before I check on things. Changes don’t happen right away. Finally, the air mix indicator can be confusing. ”Max” and “Min” refer to the amount of water in the mix.