On the subject of lighting, there is another issue I should like to touch on, as it, too, is clinically relevant: Fish require sleep and a lack of sleep contributes to the cumulative effects of chronic stress. While they most certainly do not close their eyes, fish which are deprived of a natural cycle of light and dark do not perform as well as fish which are privileged to sleep in darkness. Indeed, fish deprived of darkness still ‘sleep’ albeit no where near as beneficially as the fish with a night and day cycle.  The best lighting interval to emulate will provide bright lighting for 16 [sixteen] hours per day and 8 [eight] hours of darkness at night. The longer photoperiod will ensure a healthy carpet of green algae and therefore, lower Nitrate levels, which will soon be discussed in detail. If the algae become excessive, a Plecostomus (type of scavenger fish) will do a handsome job of algae reduction. 