:𝐃

They don't really have a habitat. Regular run-of-the-mill goo ponies like Tremble thrive anywhere there's plenty of access to water, sugar-based food, and that has a moderate temperature with places to escape the hot sun in summer and the cold in winter. Forests, caves, monster-filled dungeons, they can go anywhere like that since they can get into almost anywhere and have zero predators. They're adaptable though, so there's a lot of weird subspecies of goo ponies that tend to thrive in very specific habitats. Oil-based ones that live under water but are highly flammable, acidic ones that live in dumps or industrial areas and thrive off of chemicals and pollution, aggressive jet black ones that live in Tartarus and feed off of magic drained from other creatures, and even core slimes that are more intelligent and have heartier bodies, but have a highly vulnerable nucleus that they need to protect :D