Drywall compound skim coat number two. I think three might (!) do it.

EDIT: P.S. I’d ordered two bags of Organic Choice potting soil for the tanks, but Amazon sent me three by mistake. I called to tell them, and Customer Service said that because it was only $9.99, I could just keep it. I know it’s because it would cost them more than that to ship a 32 pound box to their return centre in KY, but it’s still cool. I’ll take a big bag of free dirt any time!