Why must fish randomly pick on and kill other fish?

[bamf25]

This is really the first time this has happened to me. I purchsed 4 weeks ago 2 purple firefish for my 120g dt. They had been together at the lfs for 2 weeks, went home in the same bag, and were in my qt together. These fish had been together for a fair amount of time. In qt they were both eating very well, I had hints that the other fish may have started picking on the other like 1 week ago, when I noticed some fin damage. Today what had been a healthy fish just died, its fins looking very tattered. The other fish looks perfect. I fully realize firefish can fight on occasion, but for 4 + weeks they had shown no sings of aggresion.

Frustrating.

 

[Recty]

It's how they ensure they get food and breeding chances. You eliminate the competition.

 

[reeferstace]

This wasn't "random". Fire fish are known to kill each other unless they are a mated pair.

 

[snorvich]

This wasn't "random". Fire fish are known to kill each other unless they are a mated pair.

Exactly. At least in the long run. In the short run before established, you can keep 20 of them at the LFS because none can establish territories.

 

[OodleyBoodely]

...and the reason they get killed in your tanks is because the loser can not get out of the winners territory.

 

[MrTuskfish]

Just nature at work. Even some plants will kill competitors.

 

[Agioniko]

Survival of the fittest corals love to do it too!

 

[Monkeyfish]

Exactly. At least in the long run. In the short run before established, you can keep 20 of them at the LFS because none can establish territories.

I think this a very important concept that many overlook or don't understand. People see 2 fish in a tank at the LFS and figure, since they're hanging out together those 2 fish must get along. The vast majority of tanks in the LFS are set-up to display the fish which means there are little to no decorations, rock or substrate in the tank. Add this to being "crowded" and fish aren't able to behave naturally. They can't make a burrow or establish a territory so the just kind of "hang out." Then when they get into your display they revert to type. Presto chango no more Mr. Nice Guy and you get dead fish.

The other common mistake is not taking into account the reproductive maturity "level" of the fish. Fish that were friendly as "children" can become more territorial and aggressive once the they reach reproductive maturity. Many fish species shoal when juveniles for protection, but become territorial when they reach "adulthood."

 

[MrTuskfish]

..........then there'e the entire concept some folks have of SW tanks, "lots of little fishies playing together". That isn't nature. A fish's teeny brain in only concerned about a few things: reproducing, eating, & not being eaten.