how do i know?

Question
how do i know if my tiger oscar is male or female?

Answer
Good morning Maurice, thank you for your question.

It is notoriously difficult to sex oscars. Males are usually larger than females, but without a comparison, this is not helpful. Venting is the only reliable technique.

Here's an excerpt from an article online:

"Before continuing, it is important to discuss sex differentiation in Oscars. Visual identification of sex based on any external characteristics is very difficult. Various theories such as degrees of coloration and aggressiveness, the shape of the head, spots or color on the tail or gills, and others have all been tried, but with limited success. The only sure way to sex an Oscar is to look underneath the fish. To the rear of the fish's anus, is the sex organ. In the females, it is a small hole. In the male, it is a phallic appearing outcropping. However, these are not readily noticeable without magnification, and holding a fish upside down under a magnifying glass is difficult at best."

That sums it up the best. You can read the rest of the article here if you are interested:
http://www.aquariacentral.com/articles/oscar1.shtml

Good luck!
Nicole