Yellow Tang Help!

[Johnny Reefer]

I don't know...goin' out on a limb here, but the major micro-bubbles makes me think of "Gas Bubble Disease", but then I think torn fins are not conducive to that.
I have been told, however, that most Reef inhabitants do not like the micro bubble thing goin' on. I suggest you resolve that.
Does your return have an anti-siphon hole drilled in to it?
Is the hole above the water line?
The hole should be just below the water line. This will eliminate your micro bubbles.
Providing adequate surface agitation, (with a powerhead,say, directed upward), will be sufficient for gaseous exchanges. You do not need micro-bubbles for gas (O2, CO2, Nitrogen) exchange.

HTH and cheers,