By using a group of pets with abilities that compliment each other, players can often find working strategies for clearing levels faster in Adventure, Challenge, and Time Trial modes, or increase the collection of shells in the Virtual Tank's screensaver mode.
Amp & Angie
Most notably in Tank 4, players may accumulate an excessive population of guppies that can benefit from Amp's electrocution ability, producing several diamonds. Because electrocuted fish leave behind a corpse, Angie is able to revive several of the recently killed fish. Presto may be used as a second Angie to maximize the amount of returned guppies.
Clyde, Nimbus, & Seymour
Seymour's ability to slow down the speed of money dropping to the ground and Nimbus' ability to bring money back to the top of the tank give Clyde a lot of leeway in collect large amount of money. If the player is able to use four pets, Meryl may also be desirable for her ability to increase the amount of money fish drop.
This group of pets can be especially useful for players who are able to house seven pets in their Virtual Tank, nearly ensuring that no shell ever disappears at the bottom of the tank.
Itchy, Rufus, Gash, and/or Stanley
Having multiple pets that are capable of inflicting damage to aliens may shorten the amount of time a player spends on a level. Notably, Itchy, Rufus, Gash, and Stanley are the only pets able to do so. As Gash's price for fighting is an occasional guppy meal, Prego may also be used to mitigate the cost of his services.
Wadsworth & Gumbo
When aliens attack, Wadsworth and Gumbo will attempt to keep fish protected with their respective abilities. Wadsworth will fall asleep when all large guppies in the tank die, leaving small and medium guppies vulnerable, but with Gumbo keeping large guppies away from aliens, the chances of all guppies surviving increases significantly..
Prego & Zorf
Especially useful with new players, Prego will help keep the guppy population afloat for players prone to losing some during alien attacks. After some time, the amount of guppies produced can quickly turn overwhelming, providing Zorf an opportunity to help the player in keeping them well-fed.
Likewise, some pets are not as well-coordinated when placed in the same tank.
Stinky & Nimbus
Presumably, a player will have mostly guppies and carnivores in their Virtual Tank near the beginning of game play. Zorf, Prego, and Stinky are an effective combination to feed the fish, encouraging them to drop money and allowing Stinky to collect it.
With seven pets, a Money Collection team can be introduced to the tank to prevent as many shells from disappearing or an Alien Offense team to used with the Alien Attractor.