hi, after my last post are tiger oscar has settled in nicely, and has been moved into a bigger tank, with a 6" catfish, and has been doing great, but today we went to a friends who had this poor oscar in a box, had been for nearly 2 days, as he didnt realise that oscar was sooo big, so didnt want to put it in his tank of mollies, so i couldnt leave the poor oscar in the box any longer, so bought him home, and put him in the tank with our oscar, well, they have only been in for 5 mins, and ur oscar is bitting the new one and they are both "quivering" as such, are they fighting? they are also swimming with mouth open. any help greatly appreciated, as really dont want to see either of them get hurt. and dont have a big enough tank spare to seperated them, only have a spare 35g tank that i can put one in if it a real emergancy, and try and rehome the new oscar tomorrow.

thanks for any help. jade.

Could you describe the behavior little more in detail please? Do they hang around with each other at all? If not, then I would say this is more than likely an aggression problem. Your tank is tightly inadequate for two Oscars are you really do need to find another home for it as soon as possible. Anyway, hats off to you for doing your best to rescue, you just have to find a suitable home for it now.

hey there!
Oscars seem to communicate through the quivering and shaking.
Plus the open mouths are a way of impressing the other oscar.
It's a common thing when a new oscar is introduced in an existing oscar habitat.
It's very hard to tell wheter things will turn into agression, or that the fish will get along eventually.
This is the introduction of my Tiger O in the red oscars territory:


If you have 2 females or a male and a female, they will portait this behaviour to establish a pecking order.
When you have 2 males, this behaviour may turn into lip locking and real agression.

In my case within some days the fish acted like this:



keep a close eye on the 2 of them, to see where the behaviour is leading.
Just be prepared to step in and act if any real agression starts to show.

thanks for the replies. the first video that was posted is like the same as ours are doing, our first oscar to the new one. the new one doesnt seem to be taking any notice of him when he is doing this, evey now and hen they do stop and swim next to each other, and ignore each other for a few mins, then its back to the pushing (bitting???) just worried that our oscar will hurt his new one. our tank is 90 gallons, so is too small for 2 oscars, but i couldnt leave the poor thing in the box, i had to take it home, and thought it be a better option to put it in the larger tank, rather than in the 35 gallon tank, until something is sorted, but i have the 35 gallon tank cycled (has being used as a breeding tank, and to wait for fish to be big enough to be put into our small fish, fish tank, so if they get too bad il take him out and put him in there for the night.


hopefully it wont come to that and they will get along, but just in case. any way .thanks for the replies. and i will be keeping a very close eye on tehm tonight.

Its normal for this sort of thing to happen when adding a new oscar to a tank. I wouldnt worry unless one gets beaten badly or is miserable (hiding all the time)

If an oscar gets beaten and you are not sure if it is badly beaten, then post a pic and we will be able to tell you if its bad

3 oscars are not good to be kept together and aften ends in aggression andn injuries, sometimes death. Also 3 oscars in a 90g is reallt too many so you will have to look into rehoming sooner or later. Better sooner before you become attached to them, which makes the decision even harder