I've seen many tosakins for sale and most of the tosai usually has very little flip or no flip at all in their tails. The Thai people has developed their own line in which the tosakin can have nice tail flips at a very young age...but most of these fish do not grow up to be as beautiful as the japan-raised tosakins. Most of the tosai tosakins of japan also have very little flip and some has very nice flips too but sometimes even the "little flip tosais" tend to win the tosakin shows in japan when they reach the oya stage...and they've transformed beautifully. I'VE been doing some observation and through my own experience keeping this variety i've concluded some ways to obtain nice tail flips: 1. Keep them in green water, so that we do not have to put any filter or air stones that can increase the water current that can spoil their tails.(the algae particles releases oxygen)(basic) 2.Keep them in shallow water so that they won't have to balance themselves (floating at abnormal angles, flipping and toppling)and swim hard which can also spoil their tails.(basic)(ideal depth for tosais: an inch higher than the height of water needed to fully immerse their bodies) 3.Do not mix them with other goldfish varieties that can swim faster than them. (so that they won't have to fight to get food which results in strenuous swimming moves that can ruin the tail)(basic) 4.Feed them bloodworms to increase colour and its easier for them to obtain food.(If u put them in shallow water you'll see that its easier for them to feed at the bottom of their bowls than at the surface...cause they'll usually miss the food due to their clumsy swimming style). 5.Separate tosakins with beautiful tails from the ones with the less quality tails to lower the fight for food.(tosakins with nice tails swim clumsier and slower than the ones with less quality tail.) 6.Catch them using basins or containers not nets that can also ruin their tails if done frequently. 7. Do not overstock tosakin bowls...give them enough space to swim freely. 8.If u are desperate enough, i've been told by a tosakin breeder that by putting tosakins in a small bowl it can increase the rate of growth if their tail thus developing the flip..but the body of the fish will not grow or they'll grow very very slowly. I 've done this..it works but u have to set the duration of putting in these containers, maybe 4-6 months so that the fish won't get stunted. THESE WAYS ARE THE WAYS THAT I'VE DONE AND SO FAR IT WORKS FOR ME ANd i don't know if it'll work for u guys but please give it a shot.