Do you know what lake he wants to stock the fish from? Because if he wants to go with Malawi id suggest A fosso and blue dolphin hap setup. He could also do a really nice peacock display in a tank that size. Lastly, if hes going for the cheapest possible tank he could have a crazy amount of mbuna in there.
Then there are tanganyikans. Waaaaay more options with this route.
If he wants action and activity I'd suggest:
Tropheus
Petrochromis
A giant colony of neolamprologus brichardi. (they're small but they have a really cool way of raising their families. I've also seen a HUGE tank with just them in it and thought it was a waste of space but when I looked at it for a while it was really a nice tank.
For a relaxing, peaceful tank:
Frontosas. A fully grown dominant male frontosa is a sight to see let me tell you. Go with blue Zaire's if you do frontosas.
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