I know I talk alot about blackworms, (I know I talk a lot anyway)
But I have been feeding these things to my fish since Nixon was President, (just after Lincoln)
They are filled with the correct oil our fish need and I personally would not be able to have a tank of breeding fish if it were not for them. Any fish I want to get into breeding condition in a couple of weeks I just feed it live worms. (Blood worms are not worms and it will not work) Live worms are cheap and available in most pet shops, on the east coast anyway.
They only live about ten seconds in saltwater so they need to be target fed.
But another use for these fantastic oil filled creatures is for feeding corals. I feed these to bubble corals and any type of cup coral that normally will eat. A couple of worms on their disk causes the animal to slowly close up. Of course the fish gobble up the worms fast so I have to trick the coral to close by touching their outer rim. When the coral closes enough so that there is only a small hole left, I shoot 15 or so worms in there. Then the coral closes fully and re opens in about 45 minutes with a big smile on his face. Well somewhat.
Here he is just after a meal.
This is the same animal, but this picture is old, the coral is almost twice this size now which is about 9" across.
Of course one of these helps greatly and I could not have a reef without it.
I also feed Bubble corals with this method. I just shoot a few worms between some large bubbles and some tentacles start to emerge. Then I shoot a few worms in a few different places. The corals open larger and much better looking.