The pellets that you feed your sea monkeys, or plankton as you called it, is primarily algae. If you place your sea monkey container under grow lights you can grow your own algae in the container that the sea monkeys will eat. I enjoyed watching mine go up and down cleaning the glass. If you start the aquarium well before you add the sea monkey eggs, you can have an established algae food source ready and waiting for them. I raised them until they overpopulated the container. To avoid this, split them up as they get crowded and keep their water on the cool side and oxygenated. I would use a bubbler stone in a sieve on the water surface so you don't create undo water currents and cause a sea monkey merry-go-round. Cool water holds oxygen better than warm water and I would put the bubbler on a timer to run for an hour a day or as you think necessary.
Your sea monkeys are probably Artemia nyos, a type of brine shrimp. Do you know what the aqua dragons are called?
Sea monkeys are a salt water creature and need to live in something like sea water. I found a suitable mixture was to add 1 Tablespoon Sea Salt and 1/8 teaspoon of baking soda to a liter of untreated water, I used well water or rainwater. I enjoyed watching mine go through their life cycles but I didn't use a bubbler and under the plant lights in the summer they got too hot and ran out of oxygen in the stagnating water. Until that point though, I really enjoyed watching them and they certainly added interest to my plant stand. If you want another challenging prehistoric creature to raise, look up Triops.
My father always said I had ants in my pants.