To determine suitable conditions for incubating Japanese eel Anguilla japonica eggs in 100 L tanks, we investigated the effects of different aeration and seawater exchange rates, and stocking densities of eggs on the hatching and survival of hatched larvae 6 days post-hatching (dph). The optimal aeration and seawater exchange rates required to be adjusted to 0.2 L/min and 0–2,880％/day, respectively. Aeration rates > 1.0 L/min significantly decreased and increased the percentage of hatching eggs and hatched larvae with skin injuries, respectively, suggesting that high aeration rates would cause the death of hatched larvae by physical contact with each other or the tank walls. Furthermore, no difference was observed in hatching and survival of hatched larvae 6 dph between low (approximately 5×10⁴ eggs) and high stocking densities (approximately 45×10⁴ eggs) in tanks with seawater exchange rates of 720 and 2,880％/day. These results suggest that aeration and seawater exchange rates of 0.2 L/min and 720–2,880％/day, respectively, are suitable conditions for incubating approximately 50×10⁴ eggs stocked in a 100 L tank.