Don't know what little oddities they might have. They're pretty straight forward. Only issue I had was a couple months ago the pump stopped running, disassembled it, cleaned it a but, reassembled, still wouldn't run, disassembled and reassembled it again, wouldn't run. Tore it apart and started looking for somewhere to buy a replacement...Reassembled again, running fine ever since.
Never seen any microbubbles.Oddities like micro bubbles do to media placement etc.
How long has it been up and running?
Love my FX4, 5, & 6. The red media 1/2 trays are nice that came with the FX6. You can buy them off Amazon and add them to any of the above. Never had micro bubbles, really like the endless options to add any media one could ever need. Good for adding current too.