Guys, my '05 TZX200 came with oxygenators in both wells. they are wired directly to the batteries with no switch - (I assume this is because the water might act like a switch??)

Anyway, i'm not seeing any "gray" mist / bubbles off of them. do they get old?? Can I take them apart and clean them?? How do I even know if they're still working?

Any help would be appreciated!! Thanks.