www.liveaquaria.com Be advised though that they are extremely territorial and get rather aggressive as they grow and age, particulary with fish of the same body shape. Mine is constantly chasing the tiger barbs in my semi-aggressive tank. She even chased an SAE out of my other tank before I moved it into the semi-aggressive tank and the SAE died.
I have heard they can be aggressive.. Mine is extemely timid now and he is in a peaceful tank. He is one of the best looking rt I have seen (very bright solid black with a bright red tail..no grey spots) I've had him in the tank the same amount of time as all the others. I added a rainbow shark about 3 weeks after him thinking there would be enough room for two in a 55 gallon tank. Not the case....The rainbow did nothing but harass him so I gave the rainbow back to the fish store. The rts had lost all its color and appeared stressed for 1 week after. He is now back to his bright colors but still stays hidden most of the time and does not appear to be growing. However he looks and acts like he is feeling great right now. Have you used liveaquaria for ordering any fish.. It is an interesting site...but I would think ordering fish unseen could be risky. I have read about how they deliver and how they recommend to acclimate them..but i would think they would be really stressed shipped as single orders...
Most RTS start off pretty passive, but they get aggressive as they grow larger and older. Sorta like people getting crotchety in their old age. Mine was in my peacefull community tank for quite some time until she started growing bigger than the other fish. That's when she changed, almost overnight. Extremely territorial now, even in my semi-aggressive tank.
As far as liveaquaria, I haven't personally ordered from them but know others who have and have been very happy with their purchases. They are a subsidiary of Drs. Foster & Smith, who I get a majority of my fish and dog supplies from. The only time I had a problem was when FedEx lost a package and Drs. F&S immediately shipped me a replacement at no charge and took care of tracing the lost package themselves.