Avoid vigorous aeration of the culture. Daphnia generally purify water and the fry will eat them as they grow to sufficient size. A shrimp net or a fine fish net can be used to catch Daphnia. Invert the net to feed. Over feeding of daphnia is almost never happens, but over feeding in a tank with heavy filtration might lead to problems if the daphnia die off quicker than they are eaten.
Grindal worms are a dwarf white worm.
Grindal worms are cultured in the same fashion as white worms with one major exception. Grindal worms grow and reproduce better at 72-82F. Cold will slow their reproduction. You can harvest and feed grindal worms in the same fashion as white worms. They are suitable for small to medium fish, but are too big for most fry. As with all worms the key to culturing is temperature, moisture, and medium.