I think there could be a fish exchange system. Like 50 snails for a goldfish, 75 goldfish for a whale. Something like that only bracketed over all the fish types.
I must agree with Exparte... Quality, and following should come before cost.... It's a lode of BS that there is a 1% opportunity for free users to do anything in the game other than do missions or co-op.... Give first THEN offer a "membership." Gameplay 10/10 Free play 2/10 (Seriously, Advanture Quest beats this game on free play material.)
 "GeoSketch"){kind=icon}
 "Dawn of the Dragons"){kind=icon}
 "Pingy the Ping Idle RPG"){kind=icon}
 "Secretnet"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "The Idle RPG"){kind=icon}
 "Remnants of Skystone"){kind=icon}
 "Madness Combat Defense"){kind=icon}
 "Simplicity"){kind=icon}
 "Notessimo"){kind=icon}
 "Orchestrated Death"){kind=icon}