Lighting making fish angry? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 04-13-2012, 09:57 AM Thread Starter
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Lighting making fish angry?

I currently have 3 Emperor Tetras, 1 male and 2 females (getting two more soon to make them the happy number 5). Anyway, the male has decided the right half of the tank is his and will defend it pushing back the females to about a quarter of the tank...only if my 15 Watt fluorescent bulb is on. Turn off the light and they begin to school like normal happy tetras. I have live plants in the tank so I'm nervous to just keep the light off, but I also feel like the male's aggression is causing stress on the females. Any advice for this? Am I over analyzing the situation?

Thanks much!


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post #2 of 3 Old 04-13-2012, 10:47 AM
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You need a larger group of Emperor Tetra, that is the most likely cause. This fish, like all characins, is a shoaling fish that lives in large groups. I would get another 4 or 5 to make a total of 7-8. However, no mention is made of tank size...this fish needs a group but it also needs space as it is an active swimmer. At least a 30-inch tank. Then up the numbers. If you don't, this behaviour of the male, which is perfectly natural, will stress the females and may kill them eventually. Male Emperors drive females hard, I know, I have a group of 12 in my 90g that I raised from fry.

The light really has no direct relation to this, it is normal characin behaviour for this and many other species. But having said that, bright light is not appreciated by this or most forest fish, so a cover of floating plants is advisable.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #3 of 3 Old 04-13-2012, 06:57 PM Thread Starter
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Good to hear, thanks Byron. Ill be sure to up their numbers a bit and Im glad to hear I dont simply have an overly aggressive male.

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