The white fish is swimming upside down more now than last night. Before I fed them tonight, he was swimming normally. As soon as he ate the food, he became unusually buoyant, like an underwater balloon. None of the other fish in the tank seem to have this problem.
I noticed him struggling to swim down to the bottom last night after feeding, and as he tired, he’d bob to the top of the tank, slowly rotating until his belly brushed the surface of the water, then seeking to right himself in a frenzy. In all other respects, he appears healthy.
But as he tires, he swims upside down more and more. I am reasonably certain the white fish will follow the call of an impossibly beautiful black fish looming
in the distance sometime in the next couple of days.