I went to my local grocery store and was trying to pick up tilapia and shrimp for my rays. And I was told my the seafood guy that it would be a risk feeding the stuff they have due to a possible contamination and where it comes from. Is there any truth to this or is there a certain brand that may be safer than others? I'm currently feeding black worms, ghost shrimp, bloodworms, and finally pellets. I wanna cut out live completely to cut down cost. Or maybe just occasionally.