Well, there is no true way to just "cut" a tank into a different regime without some fleeting consequences, but cutting the lighting intensity (NOT DURATION) is the first place. If that is not an option as a result of the wattage and the complexity of the fixture, you can raise it above the tank more and make it less effective by sheer distance (decreasing intensity by losses as opposed to cutting the wattage).
I would do this slowly if possible. Will save on impacts to the plant life.
If your desperate, just go for it. Will get funky for a bit, but lower light is always a better option if your going to neglect things by happen stance.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.