Is there any visual way of telling weather you have a male or female?

i usually catch them ONCE turn them over and very carefully open the "port" .....thats realy the only way for me to be absoloutely sure !!!!BUT I DONT RECCOMEND ANYONE TO DO THIS IF THEY HAVE NOT GOT VAST EXPERIENCE OF CATCHING HANDLING AND SEXING LARGE FISH !!!!!!!!!!!!!!!!!!!!!!

"Venting"is really the only way of sexing Oscars. However, you got to know what you are looking at, they have two holes which are slightly different on the male and female. The female will have two holes, one slightly bigger than the other, the males holes will be the same size. Like what has already been said, I wouldn't recommend doing it unless you are extremely confident handling fish out of the tank. Handling large Oscars out of the tank is not easy.

Thanks!

After moveing my two into a bigger tank I don't think I'll be checking thier holes. They are scraping more aggressively than before so I will probably have to seperate them. Keeping the lights off seems to keep the peace. I was hopeing to find new compatible tank mates. Any more suggestions?

normally, it is difficult to tell the sex orientation of an
oscar. but as bgh and ofl said... there is a way but difficult
to establish..... better off to avoid confusion. in reality,
the male code is oo while female is Oo but it requires familiarity
to be perfect, otherwise, do not give any hint at all. later on, you
will become liar if you mis-diagnose them.