Have anyone here keeping 2 Asian aro in the same thank? I am thinking of keeping one super red and HBRTG together and they are pretty much 9". I have seen people keeping 1, 3 or more then that but haven't heard of anyone having 2. If I do they are not going in the same tank together. I already had 1 and thinking to buy another 1, so I afraid the first aro might not like the new guy.
A typical answer is that you should not do that as 95% of chance they will fight. From my experience, I would guess the RTG would attack the red.
however, if you have a 90G tank, you could put both arowanas together with a divider (galss or acrylic) in between. Once they are kind of settle down a bit, you could take out the divider for a while (let's say 5 minutes) in your first try.
If they fight, separate them. If they don't. next time you can take out the divider for a longer time.
Bottom-line is that you might be the 5% lucky person who can do that.
Unless it is a pair, usually it will work better when one Asain arowana (RTG / Red / Green / X-back) makes with a non-Asian arowana (ie silver or black but definitely not Jardini)
In any case, enjoy your new arowanas!!!