arent sea monkeys fresh water rather than salt water. arent they also called fairy shrimp. could be wrong.
Nope, sea-monkeys are literally the same as brine shrimp,
Artemia salina. There's lot's of recognised species, though it's under debate whether they should all count as different species. 'Fairy shrimp' is usually what freshwater anostraca species are referred to as, though by most definitions 'fairy shrimp' is the common name used for all species under the order anostraca.
You can buy a Thai species of freshwater fairy shrimp off eBay, and you can get packets of detritus containing cysts of various random American species from a few different German websites. Some of the species commonly encountered get pretty large too, I've had a few beaver tail fairy shrimp that reached nearly 3".
Not sure if it was posted but it is a better option to hatch your own because the packaged Sea Monkeys contain no nutritional value at all for your fish
Not true, sea-monkeys are the same thing - they contain the same nutritional value as all the others you can buy. The nutrition fish get from brine shrimp is apparently pretty low, though I've heard the opposite too. However, they are great if you gut-load them first, spirulina powder is ideal for this.
It's just that the sea-monkey kits are
by far the least economical way to hatch brine shrimp - so it is still a better option to hatch your own.