Can i feed my goldfish live brine shrimp? Is it healthy and how much? My fish is getting picky?

Using brine shrimp as a supplement is fine, but it shouldn't be his entire diet or he will end up with health problems. If you were to supplement the diet with this, (and you can try mysis shrimp and bloodworms too), with a good veggie flake like HBH or Omega one, you'd have a nice well rounded diet.