Tank has cleared up considerably. I saw a little brittle star, an amphipod, and a tiny bristleworm so far.
And this giant mussel. I don't expect him to live but I placed him so he can open and not move my rock. He closes every time I open the stand drawers.
Upgraded that little Tupperware to a ~3 gal sterilite container as this tank is using up to 1 gal a day of RO.