Gifted for free from SaltyRedBird
Pink betta fish: Prince - arrogant, stuck-up, somewhat of a bully. Thinks he is God's gift of beauty to the world. The closest he comes to loving anything besides himself is adoring that Mirabelle adores him.
Yellow dwarf puffer fish: Pico - very goofy and childish, often puffs up just for fun, which bothers everyone else a little since there is not much space in the tank
Orange and black koi fish: Ulysses - quiet and dignified, rarely speaks, but when he does speak, it is cryptid and philosophical
Red spiked starfish: Penelope - somewhat tsundere, has a crush on Ulysses, but acts coldly towards everyone in the tank, including him.
Purple guppy: Mirabelle - in love with Prince, though it isn't reciprocated. Follows him around a lot and agrees with almost everything he says. Sighs dreamily at him a lot. He's too wrapped up in himself to notice. He's kind of clueless.
Ramhorn snail: Monochrome - Crush on Penelope, has no clue that she likes Ulysses.
All of these fish are quite small, some smaller than their natural counterparts.