For me, I never hoard inks. When it's gone it's gone. Use it an enjoy it.
KN site still lists all their custom inks except Tanna japonensis, "Evening cicada". So perhaps it won't be made again in the near future.
When I think of colors of aquatic creatures, I think they are somewhat bright, or even shimmery, such as the scales of fish. So it'll be interesting to see what is created.