My fish became depressed after I added pacu fish in tank.

I have 3 remaining Parrot fish, one parrot is already depressed other two fight it all the time. To improve this condition I added 3 small pacu fish but after a week all the parrot became depressed they just sit on bottom doesn't eat properly as well. I removed pacu into separate tank but parrot is still same.
Any idea what happened to them they are older than 2 years.

 

It would have been better to remove the one that was being attacked. Were the pacus quarantined? They may have introduced an infection of some kind and the parrots are now unwell.

You do know that pacus get huge, up to a meter in length?

 

i agree with TClare above, how big is the tank the pacu are now in and how big is the tank the parrots are in??

 

The dimens of Parrot tank is 1.5 ft x 3 ft x 1ft rectangular tank. I have added fish ant itch and general aid medicines and waiting to see some improvements. Pacus are in smaller tank they are little as of finger size and looks health.

edit: I change 40% water every week.

 

um, the parrot tank is a bit small for them, I would recommend at least at least 170 litres for parrot fish, which is around 45 gallons, with multiple parrot fish I would say you need a 55 gallon, your tank is small for those types of fish and can contribute to your fish being depressed.

 

Pacu is the closest relative to Piranha .
Not the best tank mate and your yank is too small for the first 3 fish you have .