There are so many variables between tanks it's not possible to suggest X Y Z for a given size of tank unlike say what manufacturers try to do with say their skimmers, sure they will just quote a ball park figure as in between two stocking levels. With Oxydators we also have to consider the animals we keep as well as stocking levels and just as importantly how much and how often we feed. A lot of information is required to best advise how to run an Oxydator to get the best out of it. Now compare that with an ozoniser with which you are often advised to run it with a redox controller with all tbe extra cost and servicing, calibrating and replacement of the probe. If there is one thing worse than no information it's the wrong information and if a redox controller plays up there csn be not so nice consciences. Once you have an Oxydator worked out to optimise it's potential which in truth isn't so difficult all that is required is to refill it now and again and you can easily work out the timescale for that.