Hey Will, here's something to consider.... I have a 135 which is same footprint as a 150 (6 ft x 18"w) but just a couple inches shorter in height. My stock is 2 red severum, 6 angels, 4 Bolivian Rams, Rummynose, cardinal tetras, Dennison barbs and an assortment of cats (Raphael, S.A. bumblebees, bn plecos). It's a great tank and I love watching it because there is always something going on. There's a good harmony in the tank. Your dad could do something similar and I think as a beginner would get a lot of enjoyment from something similar. Just a thought.
Here's a couple pics from my tank.

Here's a couple pics from my tank.
