A group of goldfish is called a trouble, a cheeky collective noun that plays on the goldfish’s reputation as a messy, mischievous tank companion. Despite their small size, goldfish are notoriously enthusiastic diggers and grazers, constantly stirring up substrate, uprooting plants, and rearranging their tank decor in search of food.

Goldfish are also famously poor at portion control. They lack a true stomach and don’t have an off switch for eating, which means a “trouble of goldfish” can quickly turn a peaceful tank into chaos if overfed, clouding the water and creating extra cleanup for their owners. Add in their habit of nibbling on tank mates’ fins and constantly rooting through gravel, and the “trouble” label starts to feel well earned.

Like many goldfish collective nouns, “trouble” leans more playful than scientific, but it captures the good-natured chaos that comes with keeping these lively, food-obsessed fish together.