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Discussion Starter · #1 ·
A question: does it negatively affect the fish if one were to switch off all the lights at the same time as opposed to having each light on a different timer and swiching them off gradually?
 

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I think if the room is not dark, it would be fine to have both lights turn on. I have two timers but the fish are all actively swimming so I don't think it would really matter. If it is really dark in the room, you might want to turn on a lamp beside the tank so they know, daylight is coming soon.

Oops, I didn't read your question carefully enough, I have two tanks that the lights go out all at once. They don't seem to be bothered at all.
 

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I used to watch my fish as the lights went off, because I used to control the lights myself. They "jump" when the lights either go on or off. It looks like something to avoid, but I have never seen any problem result from it. Now my timer turns the lights on and off and I rarely see it happen, so it doesn't bother me at all now.

Once I experimented by slowly raising the light fixture so the light dimmed slowly instead of abruptly. The fish were bothered a lot more by that. I tried just rotating the fixture to gradually dim the light. They were also bothered more by that than by just turning them off. If you put yourself in the position of the fish, they see this bright light overhead. If it moves or changes it attracts their attention and the longer it moves or changes the more it attracts their attention. Perhaps a sudden shutoff or startup is less bothersome than a gradual one.
 

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Most fish are subject to predation at night in their native habitats. I suspect that's why they get a bit jumpy when they're out in the open when the lights go off. At the same time, what are you going to do about it? Duplicating dawn & dusk acurately is pretty hard to do.

I've had a few fish go "over the wall" at lights-out, but mostly they seem to cope just fine.
 

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I'm probably wrong but...
They "jump" when the lights either go on or off.
From what I remember fish are able to perceive changes in emi fields. Turning lights on and off would cause an abrupt change in the emi fields around the tank. The field would probably be stronger if using magnetic ballasts.
 

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Discussion Starter · #7 ·
well, I have 4 lights, each on a different timer. They come on over a period of an hour, and go off over a period of an hour. the fish all seem to settle in to their sleeping spots near the end of the last one's time. So they seem to like that. They also take a while to start moving about when the 1st light comes on.

My reason for starting this thread is that I am setting up another aquarium and want to save cost on the timers. maybe it will be better not to....
 
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