Another good question!
Well, if the tang died, I'd be back on caulerpa export duty. If micro algae or cyanobacteria came back, I'd export that. I actually have hundreds of tiny to medium sized snails reproducing and consuming micro algae now, so that seems unlikely. If detritus started accumulating, I'd probably export that with water changes. But it hasn't yet, with my detrivore community doing its thing.
Another question that I thought of is; what happens when/if the tang eats all of the caulerpa?
I was hoping to reach a tang/caulerpa equilibrium, where consumption and growth balance out. That's seeming less and less likely. On the upside, more of the nutrients I'm dosing go right to the seagrasses. On the downside, I don't have the option of an easily exportable macro. Hopefully, at some point the seagrasses will multiply to the point of overcrowding, so then they could be exported.
The day that I have to simulate a manatee grazing event, will be a very happy day!