In answer to the questions regarding cork bark, it will break down very slowly over time... but we are talking years. Perhaps not as long lasting as some aquarium suitable woods but also not the worst! It does however leak tannins and can be a nightmare for algae growth due do its deep groves and general surface 'make up'. On a side note it is also extremely buoyant and no amount of soaking or boiling will ever get it to sink. But I love it and will be using it again in the future. I hope that helps?