osacr attacking aquarium glass

Question
I have an Oscar fish that is about 8in. in length and he keeps attacking the front and back of the aquarium glass. the backside has a background on it, but on the outside. I think that he may be seeing his reflection in the glass and is getting territorial but he has been doing it for close to 2 weeks and he does for 15-20 min at a time. I recently just moved the tank and rearranged everything just before he started acting strange. he has done this before when I have changed and cleaned the tank but only 1 or 2 times and not continuously for days and days. I have another Oscar in the tank that is quite a bit younger and half the size but they seem to hang out together and are nice to each other. I don't  know if they are male or female. (by the way how do you tell?) I was just wondering because I have read that they get aggressive and territorial when they have laid eggs, but I don't see any eggs. Well any help would be appreciated. Thanks, Dustin

Answer
Hi Dustin,
  This is quite normal for an oscar.  It could be because they have laid eggs, but it would be quite normal even if they hadn't laid eggs.   Oscars are highly territorial fish.

   There is no way to tell male from female oscars -- they are what we call monomorphic, meaning that males and females look alike.

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>