# Cannibalism?



## fishteacher (Oct 6, 2017)

Hi everyone,

I had 8 red belly piranhas in a 100 gallon tank. They lived happily together for over a year. However, 2 months ago they attacked one of their own and I was down to 7. Today, the attacked one again and have killed another bringing my total down to 6. There have been no major changes in diet. Why is this happening and is there anything I can do to stop it from happening again?

Thank you!!


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## timmy (Mar 29, 2004)

Very common to happen with piranha. Any recent changes to the tank and or feeding habbits?


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## newtripoli (Aug 8, 2009)

fishteacher said:


> Hi everyone,
> 
> I had 8 red belly piranhas in a 100 gallon tank. They lived happily together for over a year. However, 2 months ago they attacked one of their own and I was down to 7. Today, the attacked one again and have killed another bringing my total down to 6. There have been no major changes in diet. Why is this happening and is there anything I can do to stop it from happening again?
> 
> Thank you!!


Do you have the tank grounded? Mine did the same thing when they got around 6-8", each one died till I had 1 left. We believe this was from adding a new tank light, but I never grounded the tank, and I tested the water with a volt-meter, it was getting around 5amps! We believe they got agitated, and or, stimulated electrically, causing aggression.


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## Ægir (Jan 21, 2006)

newtripoli said:


> Do you have the tank grounded? Mine did the same thing when they got around 6-8", each one died till I had 1 left. We believe this was from adding a new tank light, but I never grounded the tank, and I tested the water with a volt-meter, it was getting around 5amps! We believe they got agitated, and or, stimulated electrically, causing aggression.


There is no way a tank light would be causing stray voltage, had to be a pump or heater in the tank. Your best bet is turning off things one at a time and finding the source... and then throwing it in the garbage / replacing it.

There is a lot of controversy with grounding rods in tanks, in some cases it will increase voltage flow and are just a cheap band-aid to a problem. A glass box of water is fairly isolated. In most homes the ground is tied to the common in the breaker panel, which can cause major issues under some circumstances. For example a lightning strike or major short in an appliance. If you had your arm in the tank, you could also become a ground (electricity flow isnt linear, and takes ALL paths to ground) which isnt a good scenario.

Like I said, its a cheap fix and you should just locate the issue and do it right.


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## newtripoli (Aug 8, 2009)

Ægir said:


> Do you have the tank grounded? Mine did the same thing when they got around 6-8", each one died till I had 1 left. We believe this was from adding a new tank light, but I never grounded the tank, and I tested the water with a volt-meter, it was getting around 5amps! We believe they got agitated, and or, stimulated electrically, causing aggression.


There is no way a tank light would be causing stray voltage, had to be a pump or heater in the tank. Your best bet is turning off things one at a time and finding the source... and then throwing it in the garbage / replacing it.

There is a lot of controversy with grounding rods in tanks, in some cases it will increase voltage flow and are just a cheap band-aid to a problem. A glass box of water is fairly isolated. In most homes the ground is tied to the common in the breaker panel, which can cause major issues under some circumstances. For example a lightning strike or major short in an appliance. If you had your arm in the tank, you could also become a ground (electricity flow isnt linear, and takes ALL paths to ground) which isnt a good scenario.

Like I said, its a cheap fix and you should just locate the issue and do it right.
[/quote]

It was the light. It was the last source. the evaporation of water from the tank, actually caused a bridge from the light, was only hypothesis. It varied as well. If you have your arm in a tank, you could be the ground, and that is why you use a ground, so you don't die/ get hurt when touching the tank if there is a short. What is a better fix than a ground? Besides, constantly checking equipment.

http://aquartaquariums.org/stray-voltage-in-the-aquarium/

Back to topic, do you think this has anything to do with the poster's behavior of fish?


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## SantaMonicaHelp (Oct 28, 2011)

Sorry to hear about that, fishteacher. Are they still eating each other?

-Kamran


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## Ægir (Jan 21, 2006)

newtripoli said:


> If you have your arm in a tank, you could be the ground, and that is why you use a ground, so you don't die/ get hurt when touching the tank if there is a short. What is a better fix than a ground? Besides, constantly checking equipment.
> 
> Back to topic, do you think this has anything to do with the poster's behavior of fish?


Not true, if you have your arm in the tank and a ground probe... You are one of 2 paths to ground and both going to take current flow, in some scenarios like a wet basement floor and no shoes, your body will take the majority of it. Ground probes DO NOT fix or eliminate stray voltage.

If you have a ground probe that is tied into an outlet (as most are, nobody pounds a dedicated earth ground) you are creating a path from every electrical outlet, light, appliance, and device in your house to the aquarium. In the main panel of most houses, the common (white) is tied to the ground (green) so you could be introducing more stray voltage... And creating more possible dangerous scenarios.

Most aquarium equipment is a 2 prong plug, not 3 with a ground... for a reason. By giving a ground you are ensuring there is a completed circuit and electricity is flowing and not just isolated. The solution is replacing outdated and old equipment that is "leaking" voltage, using a GCFI outlet and or breaker. If you want to be extra safe, use a GCFI outlet and an ARC fault breaker in the panel and have a dedicated run for your aquarium equipment.

As for OPs topic, most likely not... I would bet its a combination of things, too many fish in the tank / decor and plants that create territories / high water temp and not frequent enough feedings / low flow and not enough current or powerheads. Depending on the size and age there could be breeding pairs that are attacking the others. I would be interested to see him test his tank with a multimeter and see if there is any stray voltage.


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## newtripoli (Aug 8, 2009)

Ægir said:


> If you have your arm in a tank, you could be the ground, and that is why you use a ground, so you don't die/ get hurt when touching the tank if there is a short. What is a better fix than a ground? Besides, constantly checking equipment.
> 
> Back to topic, do you think this has anything to do with the poster's behavior of fish?


Not true, if you have your arm in the tank and a ground probe... You are one of 2 paths to ground and both going to take current flow, in some scenarios like a wet basement floor and no shoes, your body will take the majority of it. Ground probes DO NOT fix or eliminate stray voltage.

If you have a ground probe that is tied into an outlet (as most are, nobody pounds a dedicated earth ground) you are creating a path from every electrical outlet, light, appliance, and device in your house to the aquarium. In the main panel of most houses, the common (white) is tied to the ground (green) so you could be introducing more stray voltage... And creating more possible dangerous scenarios.

Most aquarium equipment is a 2 prong plug, not 3 with a ground... for a reason. By giving a ground you are ensuring there is a completed circuit and electricity is flowing and not just isolated. The solution is replacing outdated and old equipment that is "leaking" voltage, using a GCFI outlet and or breaker. If you want to be extra safe, use a GCFI outlet and an ARC fault breaker in the panel and have a dedicated run for your aquarium equipment.

As for OPs topic, most likely not... I would bet its a combination of things, too many fish in the tank / decor and plants that create territories / high water temp and not frequent enough feedings / low flow and not enough current or powerheads. Depending on the size and age there could be breeding pairs that are attacking the others. I would be interested to see him test his tank with a multimeter and see if there is any stray voltage.
[/quote]

Did you check out that link I posted with an alternative view, from which I am coming from?


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## Ægir (Jan 21, 2006)

newtripoli said:


> Did you check out that link I posted with an alternative view, from which I am coming from?


Yes I did, which is mostly about saltwater and reef tanks... where stray voltage is way more of an issue.

I still think the solution is as I said above.


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## newtripoli (Aug 8, 2009)

Ægir said:


> Did you check out that link I posted with an alternative view, from which I am coming from?


Yes I did, which is mostly about saltwater and reef tanks... where stray voltage is way more of an issue.

I still think the solution is as I said above.
[/quote]

Ok, I thought it was interesting they claimed that electric can travel from hood lights into aquariums. Also that the grounding probe seemed to improve fish health and behavior. I know salt increases current flow, but that's all; regarding salt vs non salt.

On changing equipment, I have had fish for many years. I have noticed that equipment degrades quickly. I would foresee, testing voltage every 3-4 months, and changing out equipment every 6 months or so. How often do you change yours? And if the stuff lasts long, what is the brand? thanks


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