We are building a small aquarium for the kids. We are thinking about creating a freshwater one with some angel fish most likely and then a separate marine tank as it will be good to educate the kids on the different environments they require to survive. I'm a little confused as to what equipment we'll need to create the best possible environment for the fish. From what I gather, if you buy the right plants for a fresh water tank, they should naturally help to filter the water and you don't need a UV or ozone generator to help with sterilization. Fresh water tanks however, may require a sterilization system. Apparently too, certain fish would feed off algae in the tank so if that's the case, you wouldn't need a filter as the fish will do it for you. These are just things I've been told or have read so forgive me if none of that's actually true. I'm just after some guidance so would appreciate if anyone can tell me what kind of kit we should be looking at for the both types of aquarium . We want to give the fish the best chance of a healthy life.