Lighting the aquarium
LED light are becoming increasingly popular because they are relatively cheap to run and keep the correct light spectrum for a longer period of time. A LED light may last 5-10 years as opposed to 6 months to a year for a fluorescent light.
People often ask how many hours of light their fish tanks need, and the simple answer is there are no hard rules.
It is a good idea to try and replicate nature and if you are looking after clownfish, then research clownfish and find out which water they live in and how much light they would get during the day. If for example you fish or corals are found around the equator then they will receive 12 hours of light per day. 20 degrees north of the equator and daylight will only last 8 hours.
A good solution if you have a mixed species fish tank and fluorescent lights is to start with 12 hours of light. Use a LED or blue light to come on for the first two hours to simulate morning dusk. Then turn on the main fish tank lights for 8 hours, and then turn off the main fluorescent lights and leave the blue or LED light on for the last two hours to simulate dawn. This will help fish prone to stress feel more at home.
You can buy sophisticated light set ups that will vary intensity of the lights throughout the day and follow a moon cycle. This set up is often used when people are trying to breed fish as fish will often only breed at certain times of the year.