I'm sure the combination of the two elbows restricts the return flow more than if the water just entered the tank straight as opposed to two 90 degree turns. If the elbows are needed to lower the return flow and prevent splashing then so be it. Otherwise, I'd try to keep the restrictions to a minimum and eliminate the elbows if possible. Besides, keeping the return higher and closer to the surface would help to eliminate the 'oil slick' syndrome he's experiencing.
All good suggestions from everyone. Hopefully something will work for you.
You shouldn't have a problem getting it resolved then. If you spend that kind of money on a tank, I would assume they will do whatever possible to fix the issue.