Aren't Matsukawabake like scaled Kumonryu, hence colors change/reverse in direct relation to water temperature/hardness? I haven't really noticed such changes in the Tosai even though I've left it at the dealer's premises abroad (where the climate is tropical and water temperature's relatively warm all year round) whilst considering the construction of a new pond. I bought it last January at 39cm, and it grew another 3cm in 3 months, during the last bowling/viewing; possible advantage of being outdoors in a tropical climate, or is it just the growth spurt at this stage of it's life cycle?