Light off or on spooking fish

My 6 to 7 inch bluegills in my 300 gallon system get spooked by a sudden turn off of a light after dark. Turning on the light gets a reaction but not as severe. You can hear them startled scooting and splashing around when the light snaps off. I've tried to remember to turn it off before the sun goes down but it doesn't always happen. To that end I've installed a dimmer switch, and slowly turn off the light which helps some, but if I don't go really slow at it they still get startled although not as much.

Anyone else experience this and what did you do? I'm using a soft white light bulb. Perhaps a different light bulb?


I'd like to just depend on natural light coming in from a window but there isn't enough to see in this basement room, and artificial lighting seems to promote better feeding. I thought of a timer to shut the light off before sundown, but I'm not sure how to hook it up to the electrical outlet.

I need to produce as perfect as fish as I can for my niche markets and don't want any damaged fish. I also don't want any stress if I can help it for obvious reasons.

Edited by az9, 24 October 2010 - 10:16 AM.

Very simple and inexpensive timers are available at home improvement stores. They simply plug into a standard wall electrical outlet, you plug your fixture into the timer, set the timer, and it does its magic. I'd try that.

I agree with the timer suggestion, and would like to add something.
In my tank, I have four different lights (the tank is kind of big). So to avoid spooking them, I slowly turn off the lights one by one, brightest first. It creates a kind of twilight lighting, which I leave on for about ten minutes. They do well with that.

Edit: Oh, and the fish tell you when they're ready to go to bed. If you leave half of the tank lighted and half of it not lighted, the fish will either group in the lighted half or group in the dark half. As the night gets later more and more of them will group in the dark half. When that happens, they're ready to have the last light turned off and they don't spook.

Edited by EricaWieser, 24 October 2010 - 11:17 AM.

I agree with the timer suggestion, and would like to add something.
In my tank, I have four different lights (the tank is kind of big). So to avoid spooking them, I slowly turn off the lights one by one, brightest first. It creates a kind of twilight lighting, which I leave on for about ten minutes. They do well with that.

Edit: Oh, and the fish tell you when they're ready to go to bed. If you leave half of the tank lighted and half of it not lighted, the fish will either group in the lighted half or group in the dark half. As the night gets later more and more of them will group in the dark half. When that happens, they're ready to have the last light turned off and they don't spook.

Anyone have any experience with sunrise/sunset timers?

Anyone have any experience with sunrise/sunset timers?

You'd just have two different timers, each controlling half of your lights.
First, one of the timers would turn out its lights. Then, a half hour later, the second timer would extinguish the remaining lights.

Edited by EricaWieser, 28 October 2010 - 05:43 PM.

Set your lights to go on, and off multiple times per day. Within a week or two, you will notice much less frantic behavior, as they get desensitized to the light change. I have done this recently with tilapia in my greenhouse. Worked like a charm.

Edited by Skipjack, 28 October 2010 - 06:01 PM.

Set your lights to go on, and off multiple times per day. Within a week or two, you will notice much less frantic behavior, as they get desensitized to the light change. I have done this recently with tilapia in my greenhouse. Worked like a charm.

I think I've found a simple solution for now. I turned down the light tonight (It's just one light) with the dimmer switch but not completely off. As long as I don't turn it off completely they don't startle. Didn't know Lepomids need a night light did you?