Bunibranchs are small molluscs that are about palm-sized at their largest! They're slow-moving aquatic predators, and they crawl rather than swim. Their prey, thankfully, is slower than them, as they primarily eat stationary animals such as corals and anemones. Bunibranchs are able to incorporate the stinging cells from their prey into their own skin to defend themselves from would-be predators. They breathe using the plume of gills on their back. Their simple eyes can only detect light and dark, but they have a keen sense of smell using the rhinophores (antennae) on their heads!

While bunibranchs can be kept in captivity, they're known for being extremely picky eaters. Each adult bunibranch has a favorite food, and they will refuse to eat anything besides that single favorite food, sometimes even starving to death before trying alternatives. To make matters worse, their prey can be difficult to find sources for. their favorite food seems to be based on what they ate as larvae (young bunibranchs will eat anything available to them), so some breeders have had success with feeding them only foods that are easy to come by, prompting them to pick one of those foods when fully grown.