Frozen blood worms are too large at this point. Just keep them in the freezer for now. Just feed the First Bites, a very tiny amount goes a long way. If you have a plastic tooth pick, use the spatula shaped end to get a very fine coating of the First Bites and dip it in a cup of water. You can see how it spreads across the top of the water. If you put the toothpick into the water and very gently swish it around, you will see a little cloud of food, that will be best for now. That's just practice before you feed the fry. You can then throw out the water in the cup and try your first feeding of the fry. Try for a small cloud of food. A very tiny amount goes a very long way and the packet will last a very long time. Remember to seal up the packet after each use so the food doesn't spoil. Put in less than you think they need to begin with. It may take the fry a day or two to get used to the food. Feed the same amount of times that you have been feeding already.