I have a theory... actually its more like a question... does anybody want to know?

yep ......

Why do some Oscar tails look different than others. Some look fuller and the others dont. Let me explain more by pictures... I will do that when I wake up.

Male and Female?

genetics

???????????????????????????????????????????

Thats what Im wondering vamp.

And if it is genitcs... why...

k to start with oscars are monomorphic. this means there is no way to distinguish the difference between male and female. there is a technique called venting however this is not 100% acurate in oscars and is very stressful for the fish.

and as to why genetics because all fish not are equal. they always differ in apperance be it subtle or not. like people having different shape ears or noses. they are the same but different.