Could micro bubbles be killing my cheato?

[fishmaster]

My cheato in my sump doesn't seem to be doing well. In fact it's slowly dying. I'm running a 55 with a 25 sump. I've got aprox 100 lbs of live rock between the two. For livestock, I have 3 percs, 2 blue damsels, 1 yellow tang, 1 lawnmower blenny, 1 neon goby. As well I have tonnes of hermits & snails, 1 large sebae anmone, and some asst corals. My nitrates and phosphates are very low, but you would think there's enough for the cheato. I run an 18w light over my sump 24/7. The only thing I can think of is microbubbles from my skimmer. Other than that, maybe the excessive amount of live rock is taking care of the wastes good enough that there's not enough left over for the cheato??? Any thoughts?
Shaun.