Thanks CFC and cometcattle,
it is definately not the perch, it looks similar to the leaf fish you posted a link to cometcattle, the juvenile i saw is different to that picture but i could imagine it growing up to be like that.
Thanks, thats solved my problems, im not actually going to buy any because of my oscar but at least i know a little more about them now!
dman
EDIT: thanks bloozoo2 aswel