Pets can be combined in any game mode to provide effective results and make game play efficient.
Itchy, Rufus, Gash, and/or Stanley can make disposing of aliens quick when used together. Optionally, Prego can be used to keep the guppy population slightly afloat if Gash is chosen. Presto can be used in place of Gash to reduce the amount of guppy deaths.
Money Collection #1
Clyde, Nimbus, and Seymour are an excellent set to collect larger amounts of money. Seymour and Nimbus prevent money from disappearing quickly while Clyde collects. If at least four pets have been unlocked, Meryl can be added to increase cash production.
If at least seven pets can be used in Virtual Tank Mode, these three pets can ensure shells almost never go to waste.
Money Collection #2
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.