I would defrost them first, take a small container of water from the tank and pop the frozen food in there. You can, once it's defrosted pour it through a fine net to get rid of the liquid, which is of no use to the fish and adds to the bio load of your tank
I always defrost first, and don't just dump it into the tank either - experiment and see how much you really need because if you overfeed it will pollute the tank. Common small community fish don't need more then one or two at a sitting.
How would you like a block of frozen food presented to on your plate, and were told to get on with it?
Not very nice. The same with frozen food. It would be nice if the food was first thawed to at least room temp. first
Then you could pour the whole lot into the tank if it was too much trouble to rinse the worms out in a net first to get rid of the liquid the worms were frozen in.
The fish would "taste" the bloodworm before they ever saw them because of the "bloody water"
Thawing out the food would also prevent indigestion problems in fish which is often dangerous and difficult to treat.
For my betta, I thaw the bloodworms first, then dip a plastic stirrer into the mix to get one or two on the end. I then gently place them in the water. Sometimes he actually takes it right off the end of the stirrer. I've only seen two bloodworms ever make it to the substrate.
This is perfectly normal, right? No spoiling the fishies going on at all! Nothing to see here. Move along...