The only thing about running them 24/7 is replacing the bulbs. Is 2 hours a day enough time to clear green water? Maybe eventually. However, if it's not clear by the time you come back, then I'd say it's not enough. Personally, I would run it for 12 hours a day and adjust from there. If 12 hours clears it, then cut back to 6 hours, and if it stays clear go to 3 hours, and so forth.youll be able to dial in exactly how long you need to run it for. You may find that it's a seasonal problem, and that you don't need to run the filter much more than twice a year. Or it may be a chronic issue, in which case you would need to run it most of the time, if not all the time. If it's chronic, then that means there is a standing imbalance somewhere. It's usually recommended to correct the imbalance to correct the problem, and that really is the best thing to do.... Assuming you can. It's not always easy to determine the source of the problem.