I have kept the Red Tail Shark in many different aquariums over the years. In fact, it would probably not be a stretch to say i've had this fish in 20 to 30 different setups. It is one of my favorites.
In my experience, the RTS is a rather territorial fish, generally picking a place in the aquarium that it calls home, and then defending the territory around that space rather aggressively. It will behave most aggressively towards fish with similar body shapes, and especially other RTS.
The good news is these aggressive tendencies begin reduce as the length of the aquarium increases. I found that 55 gallon tanks appear the be the ideal minimum size for a community which houses a RTS. When kept in smaller tank, it will also sometimes attack schools of fish, and may consider the entire aquarium to be its territory.
If you do decided on a RTS, I strongly recommend placing an upside down flower pot somewhere in the decor. The fish will almost always call this cave home, helping it to settle into the tank and feel at ease. Also, realize that this fish will fade color at night time, and appear almost a light gray color in the morning. Do not be concerned by this.
Finally, if you prefer a more peaceful option, the Albino Rainbow Shark
is a much more appropriate fish for most mixed communities. It is a great algae grazer, is much more active during the day, and shows very little aggression towards tankmates.
Good luck with your new tank.