| My friend, and old science teacher is in absolute love with Oscars and has kept them for years and years. I called him up using your question as an excuse, and he confirmed that venting is the best 'scientific' way to determine sexes of your fish, however, you will also be able to tell, possibly earlier, which are male and female since they will most likely pair off (dominant male and one female). Should you have one male and two females, the least dominant female will be bullied and possibly killed, so keep an eye out. Likewise, if you have two males and one female, fights will ensue. If they are all male, you will have territorial fighting an not so much pairing off (two fish fighting with one) and if all females, this will also be true but to a much less extent.
Hope this helps a little bit. |