The first time I kept an RTGG, I raised her with oscars, a small FH, bala sharks, and polypterus.
I never had problems with it attacking the other fish and vice versa.
My two current RTGG are also being raised with a couple oscars, polypterus, sevs, and geo's.
The two RTGG keep any quarreling to themselves, but have been arguing less and less as they're growing.
I based my last response on some posts I've read around the net. Can't remember exactly where because I wasn't in that 'research mode' where I save my sources, but the jist of what I read was other's trying to add fish with their sub-adult to full grown GG's with ill effect.
However, if the enclosure is spacious enough, it probably wouldn't be such a big deal.
Oh side note, Santoury, I picked up a juvie Gold/pink GG last weekend!
$10!). It looks just like 426Hemis'. I want to get more, but don't have the space. I'm saving the last slot in my current tank for a grey
gouramy.