Are you feeding adult artemia? If that´s the case, are you culturing it or buying it? If you are culturing Artemia, i would just recommend moving to a different species of anostracean, any fresh-water one. That way there would be no concerns.
It´s difficult to say how often you could feed artemia...because i doubt there´s a definitive answer. I would just say that it´s probably best to use them sparangly, alternating them with other options while still maintaining a staple basis of worms.