The beneficial bacteria is in your filter. If you don't have a filter, you do not have a cycle anyways so every time you do a water change you just start it over. Adding in a decoration will not harm it unless there is a toxin or something on it, so be sure you wash it well without soap(use water, vinegar and salt and soak it in that overnight, rinse thoroughly before adding it in), especially wont mess with an established tank. The only thing you have to worry about, is if it fits right, and if your fish/critters like it. lol
forum community dedicated to tropical fish owners and enthusiasts. Come join the discussion about species,breeding, health, behavior, aquariums, adopting, care, classifieds, and more! Open to fish, plants and reptiles living in freshwater or saltwater environments.