Aquarium furniture refers to the various ornaments and functional items in an aquarium. Ornamental aquarium furniture is often kitsch: popular examples include ceramic mermaids, 'sunken' ships and castles, and the ever-popular (but curiously misplaced) "No Fishing" sign. Another strange piece of decor is the ubiquitous plastic corals found often in freshwater tanks. (Corals are exclusively found in saltwater.)