I don't know why I've never thought to ask this before but while I was watching my Oscars yesterday, I noticed one of them like quivering all over - it kind of looked like it was shivering pr something but I don't understand what it means. I have one full grown Oscar, and 5 others that are about a year old or so - I have seen them do this before but I don't know why they do this. Does anyone know what this means, by chance?

Don't worry, you Oscar is not ill. I have observed the Oscars doing this many many times before. Since it was my breeding pair that used to do this all the time, I'm guessing it is some kind of communication between two Oscars, or it could possibly be along the same lines as why squid change color when they are in groups.

They used to do it when they rubbed up against each other. I did read on another forum sometime ago that it was a sign of aggression. Personally, I never saw any sign of aggression when my Oscars used to do.

However, keep an eye on them, I would be interested to see if you experience any aggression when they're doing this

Great white sharks do the same sharp body movements, A kind on shaking,tail quiver and head shake. In the shark world this is a warning " I am strong stay away, the boss" I have took this as oscars must mean the same. I have tried this myself with my hand. As a oscar comes close to bite me, I make my hand big(open) and shake like the fish do, the fish that was going to bite me always backs down.I know I am mad but I have to clean my tank and if I took it out every time they took to biting me it would take forever. if some of you try this please fill me in as to weather you got biten or if they backed down. make sure you dont move your hand away. Hold your ground and shake in small sharp movements. we shall see what happens??( sorry if they bite you))))

it does make sense. I still don't think it's a sign of problems in your tank because like I said, I've seen it many times before and I have never had an aggression problem. but I could certainly see how one Oscar might not want the attention at some stage. Definitely something to observe for future reference

I have been having a look around on the Internet and 80 all of the information seems to tally in with what I reckon is going on. I don't think it is really aggression, it's more likely to be the kind of behavior you will see between a male and a female. In my case, this is definitely what has been going on.

i have also noticed this behavior in my bigger oscars. at first i though it was an illness but after a while i realized that is was just when they were together. i agree that is probably just some kind of mating thing between the male and the female.

Those who know me will know i keep Channa's(snakeheads) This body shaking and head bobbing is a daily occurance in them,im with ofl it's not aggression because these things would just bite each other in half.My channa lucius brush against each other and always head bob at one another,theres never any aggression on either part.It has to be a form of communication,but i have observed the same body language before they chase the O for coming to close.But don't worry guys the oscar isn't the one that stands down.They have more or less grown up together and he rules at the end of the day,that is untill the channas outgrow him then ill split them up or i won't have an o left!!

I think you would probably have to observe several breeding pairs of Oscars but I'm in the opinion that it is more than likely a female male thing.