I cant answer the ozone question, but the mangroves are normally easy to keep, I kept them for years, I would have times where they would just start dieing for no reason and then they would come back. Im told adding iron is beneficial for them. As to there nutrient export capability, I found that the only advantage for water quality was to have LOTS of them. A few wont make any difference, but they are neat to watch and add another touch to a diverse aquarium