New additions upset the status quo?

[hogfanreefer]

Has anyone ever had the introduction of new fish cause aggression between previously peaceful tankmates?

I introduced 3 new flasher wrasse that completed QT. They were ignored in the acclimation box by everyone including the resident P. attenuatus. However, late this evening the diamond tail started getting in to it with my flame wrasse. They were swimming in circles and chasing each other for as long as 5 minutes continuously. Nothing physical but these two have been in the tank together for close to a year with no acknowledgement of each other. Thought it was kind of strange. No aggression at all with the new guys.

 

[d-man]

Yep, typically normal.
New fish =new territories.
Upsetting the balance is all. Nothing major usually happens, just some pumping of the chests.

 

[kmbyrnes]

The new pecking order is being established and even some previously passive fish may be looking to improve their social status. In most cases, it will calm down in a couple of days

 

[hogfanreefer]

The new pecking order is being established and even some previously passive fish may be looking to improve their social status. In most cases, it will calm down in a couple of days

That's exactly what happened. Everyone is living peacefully now except for an occasional short chase by my C. Cf lanceolatus after the yellow fin flasher.

 

[lifeoffaith]

I added a pygmy angelfish to my 24 gallon and she and my clown pair were at each other's throats immediately. The pygmy now owns the run of the tank, but the clown pair are holding their own. They even both got pop-eye from all the rough-housing from the pygmy, but they have both healed back up and are just ruling the top of the tank (which is where they preferred to hang out anyway).

 

[evolved]

Yes, somewhat common. Any new addition has the potential to shuffle the hierarchy.