In adventure mode, the player gets a tank of guppies each level and he need to take care of them in order to get money to reach the goal- buying egg pieces of special pets, creatures who helps the player in his game.
The player also needs to protect his guppies from evil aliens who wants to kill them. That's why the player has to use a special laser and it's upgrades, except for battles with Gus, a wierd fat humanoid alien, in those battles, the player need to feed Gus until it explodes.
There are 5 tanks, in each tank there are 5 levels (except for tank 5, where there is only one level). That means there are 20 pets in the adventure mode, because in tank 4-5 there isn't any pets.
Tank 2 - Gus, Destructor.
Tank 4 - Bilaterus.
Tank 5 - Cyrax (The alien boss of doom).