Ahhh Sea Monkeys (aka Brine Shrimp). I went a little apeshit with them for about 6 months. Got all the accessory supplements. Then I realized I didn't care all that much and let them die.
The "water purifier" is actually where the eggs are. The second packet is simply a mixture of food and dye, basically making the teeny tiny shrimpoids visible.
I had sea-monkeys. In the instructions is says only to refill the water that evaporates from the jar every however many days, because when the solution is at a higher concentration it hardens their shells. I figured I wanted my sea monkeys to be badasses so I rarely if ever refilled the water. I can only imagine this contributed to their spiraling downfall.