[Problem] To provide breeding water for anguilliformes, and a method for rearing anguilliformes using the breeding water, in order to artificially control the transformation of glass eels and the like and produce glass eels and the like in the same size and form with a shorter period until birth. [Solution] Anguilliformes breeding water containing a thyroid hormone such as thyroxine, and a method for rearing anguilliformes including a step for administering a thyroid hormone such as thyroxine, wherein the amount of the thyroid hormone to be administered changes as the anguilliforme fingerling changes from a transformation start phase (stage 1) to a transformation final phase (stage 2), and the amount of the thyroid hormone to be administered in the transformation final phase (stage 2) is less than the amount of the thyroid hormone to be administered in the transformation start phase (stage 1).
