A Varied Diet?

I have a tank with Rosy Danio's, juvenile Congo Tetra's and Glowlight Danio's. General advice, especially with the Congo's  is that they need a varied diet and to supplement their diet with frozen food such as daphnia and artemia as this is their natural food. Trouble is none of them will touch either, even when not fed for a while
They just sink to the floor and are left to be vacuumed out. Are bloodworms too big? I've never seen a fish that doesn't love 'em. Any other suggestion?

PS.. Anyone looking for a hardy, entertaining and beautiful starter fish should look no further than the Rosy Danio. Georgeous 

Thanks Sue, I got some brine shrimp today and they went crazy for it  Also got some bloodworms to try later

Thanks for the reply Colin. I've read that some people are wary of live food due to a much higher risk of introducing something nasty to the tank than frozen. Is there any truth in this?

There's virtually no chance of anything nasty coming in with live food. Daphnia, for example, will only be found in waters without fish, which would eat the daphnia of course, and in any case live food today will all have been bred in special systems, not collected from the wild. No fish, means no possibility of fish disease and any predators large enough to harm fish would be blindingly obvious just by size. The danger would come from letting the live food die and decay, then feeding it to your fish. The "danger" of live food is another myth (of many) passed down from person to person none of whom know what they are talking about.