How Long Should Fishtank Lights Be On?
Both fish and plants need a regular light and dark cycle, whilst fish do not 'sleep' like we do, they do have a sleep-like state, and plants need a dark period to rest and carry out normal biological functions.
In most cases it is best to keep a regular day/night cycle similar to the 10-12 hours a day your plants and fish would receive in nature.
Because a sudden shift from bright light to complete darkness can be a shock, it is best to turn your lights on after sunrise and off before the room lights go off.
Putting your lights on a timer is the best way to ensure a regular period - your fish will adapt to this stable rhythm and will 'slow down' their activity just before the lights are due to switch off.
Reducing the duration of light can help with controlling algae but may cause problems for plants and there are better ways of controlling algae.