Finally started adding some "real" fish!

My 50gal tank has been occupied by a bunch of danios (which will eventually be moved elsewhere) and two bristlenoses for just over two months, since it was set up. I now have added my centrepiece fish - 3 yoyo loaches - and a recent decision - 2 siamese algae eaters.
The yoyo's have already become the stars of the house, entertaining us to no end with their antics. They have also caused me a mild heart attack when one seemed to utterly disappear from the tank for a while. Also, they don't seem to be eating. They forage, but don't go after the food I put in for them (frozen bloodworms or sinking pellets). I am thinking of trying some live food for them. Any recommendations? And one last question - today one of them has gone almost totally grey, the markings fading and the base colour darkening. What does this mean?
The SAEs were in response to a niggling staghorn problem, and even in the few days they've been in the tank, they have nibbled about 3/4 of it! I am totally impressed. And they're so pretty, I love the way they hover like hummingbirds. I have named them Chang and Eng, after the first Siamese twins (original, eh?).
I also got about a dozen mixed sex guppies to start my guppy community breeder tank. We have a java moss wall growing in that has already proven an excellent fry-saver. Here's to livebearers!