In a couple of days, the shrimp loose their orange color and you won’t be able to see them. You will think they died. Have faith. They are probably doing just fine. They will grow enough to see them again in a week or so. I add more baby brine shrimp ever week or two.
After about 3 weeks they will reach harvest size. Use a course net to catch the larger ones while letting the small one through.
Supplemental feeding with green water is useful. Algae will sometimes form on the sides and bottom of the container. That is great as brine shrimp will scrape it off if they can’t get enough by filter feeding.
As the brine shrimp grow to adult size they will start to reproduce on their own. If you don’t add more baby shrimp you can sometimes see small shrimp from natural reproduction. I don’t think they reproduce fast enough on their own to keep up with harvesting. If you are using hatching water you would otherwise throw out, you can keep a steady stream of adult shrimp for no additional cost.
As the water gets cooler they don’t grow very much but they will stay alive until the water gets close to the freezing point. Because salt water freezes at lower temperature than fresh water, they last later in the year than daphnia, which I also raise outdoors. Here in south eastern Wisconsin I can harvest until mid-November in most years.
If you let the container freeze over the winter, there is a good chance the shrimp will reappear in the spring. I found it is best though to start with fresh water each spring for maximum production.