another lighting question

[inoffensive nickname]

What are the advantages/disadvantages to keeping light on 24/7 in a tank with no natural plants? 37 gal fresh. 3 mollies, 1 fancy gold, 1 guppy, 6 minnows and a CAE. It's the stock fluorescent light that came with the light strip.

I was told by a local enthusiast (not a LFS employee) that fish don't like darkness and need to have the light on all the time or they will die.

My thought is that fish don't live in the wild with the sun turned on 24/7, so when would they sleep or is light not a factor? Don't animals need to sleep?

I've searched the threads and found debates over types of light, but not over duration, except when dealing with algae. The tank has plenty of ambient light during the day as it sits fairly close to a window, but far enough away to not get direct sunlight or be affected by draft in the winter.

I asked my fishies, but they aren't talking yet.

 

[meegosh]

Well besides the obvious algae issues... fish do prefer some type of light cycle. I would recommend buying a cheap analog timer and put the lights on a timer. I'm not sure of the science behind it but I'm pretty sure you need a fairly consistent lighting schedule. This also helps the fish realize when it is time to eat - at least that seems to be the case for me.

My lights turn on about 30 minutes before I get home and the wifey tells me they all swim up to the top about 10 minutes before I get home and stay there until I get home and feed them. Even my newest additions, my 10 von rio tetras (thanks HN1 and severum!), are exhibiting this behavior.

 

[BigJim]

I think leaving the lights on all the time screws with the fish's circadian rhythm. If the fish are diurnal, they like to sleep at night and find food during the day. Nocturnal fish follow the exact opposite schedule. If the lights are on all the time, the diurnal fish won't sleep well and the nocturnal fish won't want to come out to find food. Watch your tank an hour or so after the lights have gone out and you'll see a very different place than during the day.

I've set my lights to come on at 5:00, go off at 9:00, come back on at 3:00, and go off again at 9:30. I did this because leaving the lights on all day was causing algae problems and I wanted the lights on when I'm home.

 

[cabezon]

my fish got all spazzy if my boss forgot to turn out the lights when he left for the night.