Make sure your fish are flush with cash, because they might have to pay a toll at the Penn Plax Troll Bridge Aquarium Decor This fun bridge is crafted with amazing detail with a bridge and rock outcrops. The bridge has spaces for fish to hide and swim around. Crafted of non-toxic resin for freshwater or saltwater Penn-Plax is a family-owned company in operation since 1959. They specialize in creating excellent pet supplies for animals both great and small.