Treat your gilled friends like royalty with the Penn Plax Medieval Castle of France - Small. This awesomely detailed castle is a classic piece of aquarium d ©cor that fish will love - plenty of room to hide and swim around. It's crafted of non-toxic, fish-safe resin. Penn Plax Penn-Plax is a family-owned company in operation since 1959. They specialize in creating excellent pet supplies for animals both great and small. Best known for producing pet products at affordable prices, the Penn-Plax brand is synonymous with innovation and quality, keeping your pet foremost in mind.