A method to efficiently remove residual sperm from rearing tanks to prevent water quality deterioration was examined. We conducted experiments with pufferfish Takifugu rubripes sperm. In the control, filter device without filter materials, sperm decreased to 76.6% of the initial density after 24 hours. Use of a filter device with filter materials (ceramics) halved the sperm eight hours later. Sperm density when using a foam separation device was significantly reduced to 22.5% in one hour. Therefore, we conclude that the use of a foam separation device is effective for the removal of residual sperm in rearing tanks.
