I currently have some Sea Monkeys, and they're thriving! I've always had at least one of these kits laying around, and I found one about 2 months ago and decided to try it. Well, my biggest fellow is about one centimeter long, and there are about 13 or 14 swimming around in there right now.
I don't have a pump, so to oxygenate the water I just stir it up a lot so it makes bubbles after dropping in food. So...maybe once every three or four days. They just keep mating, and having babies, and mating again...I've got little generations going on in my tank!
Sea Monkeys are really easy to take care of, you just have to make sure you put the tank in the right spot. Too much sunlight will kill them all, and too little will as well. I have mine next to a lamp that stays on during the day but shuts off at night. You also need to have the water fairly warm, or they won't hatch at all.