Of course this kills the Daphnia, so adequate circulation is required to keep them in suspension during feeding. They also will not be as nutritious as the nutrients rapidly leach out in the aquarium. Nearly all the enzyme activity is lost in ten minutes, and in an hour all free amino acids, and most bound amino acids are lost. Fish will not feed on frozen Daphnia as readily either. Trouble Shooting Culture failed completely Toxic materials in the water.
Daphnia are extremely sensitive to pesticides, metals, detergents, and bleaches.
Over fertilization with a mineral based fertilizer can also be toxic to the culture. Slow Reproduction Temperature is outside optimum range, insufficient dissolved oxygen because of dense colony. Heavy aeration, or fine bubbles can strip Daphnia from the culture. Overfeeding and fouling of the water. Insufficient food or fertilizer.