If this card is sent to the GY to activate a monster effect: You can add this card to your hand. If a monster(s) is sent to your GY, except by battle, while this card is in your GY (except during the Damage Step): You can discard 1 card to the GY; Special Summon this card. You can only use 1 "Butterfly Fish" effect per turn, and only once that turn. You cannot Special Summon from the Extra Deck, except WATER monsters, the turn you activate either of this card's effects.
