Most new skimmers will produce fine bubbles initially due to the plastics. This should subside over time. Please note though, just because there's bubbles in the tank doesn't mean your water is being oxegenated, you need surface agitation for this and micro bubbles won't cause much of this when they hit the surface.
Also bubbles aren't good for fish or corals, they can agitate them.
The skimmer isn't an MCE600 by any chance. I got one of these second hand and it's still producing micro bubbles, even with the degausing plate attached

. I was able to use 40mm PVC piping and a couple of 45 degree joins to stop the bubbles. Only problem is my tank now looks like a building site

. I'll probably get rid.