Insaniquarium.
The robot alien is a pushover. He just sits there and shoots three rockets at a time, which are very easy to destroy before they kill your fish. 2xcollectors (preserve your clicking finger)/mermaid multiple gets you an insane amount of drops. Turn your fish into star droppers, and fill your floor with the star eaters to spam diamonds. Or build whatever kind of economy you want.
This game is pretty poop-oriented. The king fish is so badass it shits diamonds. Literally.