Male medaka fish adjust the amount of sperm they release depending on the quality of the female they are mating with, as shown by a recent study. The researchers observed that males alter the duration of sperm release during mating, releasing more sperm when paired with larger and heavier females. However, the number of sperm released by males did not affect the number of eggs spawned by females. This suggests that female medaka may have ways to counteract male sperm allocation strategies and that males may not always be able to adjust their sperm efficiently. This study highlights the complex interplay between male and female medaka in the context of sexual conflict over limited sperm resources.