The way I see it, only gouramis and goldfish would eat the stuff willingly, seeing as how they're little vacuums. The other fish will probably only eat them after a period of fasting...
That is what I do with both the Tubifex and brine shrimp.
I break them up into small pieces so they will eat them..
I will say it is a riot when I put the brine shrimp pieces in.
They all go to the top of the tank to get them and with two filters the circulation is really good so they chase the pieces in circles until they are all gone.
If you have ever watched a guppy go in circles three or four times because he wants the biggest chunk, then you probably know the kind of laugh I had since moving them to the 55G.
Try holding the cube under water for a minute or two until it becomes wet. Then gently rub it between your fingers, and shake it, and the worms will separate into individual pieces. You can then stop adding them when you think enough is in the tank. Depending on your fish's' appetites, you might want to break the cube in half first.