So I decided to get another betta. The small, 2-1/2 gallon tanks are easy to clean if I can remove the one fish inside, so although I contemplated something like neons or glofish, that idea was short-lived since they'd be harder to catch during each water change. And smaller tanks can get dirtier much faster than larger ones.
My friendly local pet shop phoned me to let me know a new shipment of betta babies had just come in, so off I went.
Here is the new, multi-colored betta. He is a comb-tailed betta, the first one I've had. He seems very happy to be out of a cup and in a real tank. He is about 1/3 of the size of the adult betta.