I decided to replace my Tunze skimmer with an Aqua C Remora. I have read very good reviews of it, and I liked the hang-on-back aspect because it doesn't require ongoing adjustments as the water level changes in the tank.
I have only had it a couple of weeks, but so far it looks like a good choice. Thanks to a couple of screw ups I accidentally received two of them. And the differences between the two skimmers--that are the same model--are interesting. Click on the pictures for larger versions...as you can see the collection cup lids are quite different, as are the maze-like paths for water. I was fortunate for the mistake because I believe the first skimmer I received (skimmer B) does not work properly. It was louder, made more erratic noise, released more microbubbles into the tank, and just didn't seem to skim as well.
I don't know the reason for all of it but I have an idea that the water maze may be a reason for the bubbles and poor skimming. The maze in skimmer A in my mind works better because it comes very
close to the bottom. This makes it much less likely that bubbles will be released into the tank. Instead more will float up into the chamber below the collection cup. [For clarification the intake for the skimmer is on the right side in the photos, the collection cup is dead center, and the exit is on the left.]
I have no way of knowing what differences may exist within the PVC pipe that the powerhead connects to. This is where the bubbles are created, and therefore the source of the noise. Since the noise levels and character of noise are different it makes me think that something inside there is also different.
I think this skimmer has promise and will update if my experience begs it. But I think that the maker needs to perfect the design and/or improve quality control, because clearly not everyone is getting the same AquaC Remora skimmer.