Feeding My Striped Raphael Catfish Brine Shrimp?

Hi. I am new to the cats so I need someone to help fill me in here. I am feeding my cats Frozen Brine Shrimp. The employees @ petco said disolve the shrimp before feeding to the fish, but it breaks down into tiny pieces when i drop it in. Should I ignore that technique and just put it in there frozen so they have more of a chance to eat it? Also, how do i personally feed the fish so that I see them eat it. This is just my personal want because I like to make SURE that the cats got their food. Thank you, and please give me all the info you know!