I added a betta to my nano-aquarium. My cat approves.
Since this video was shot 2 months ago, I’ve acquired an aquarium snail and an anubias nana plant. I slowed the flow of the filter with strategic sponge-placement and the heater has been removed. It kept the water at a toasty 76, but I was fretting over it; My sister had a bad experience with a mini heater once where it malfunctioned and cooked her puffer-fish alive.