There are 2 body types and 2 fin types that cannot be produced by breeding (you can get them only from eggs or mutation), and the Twin-Fin and Silky are the two fin types. You can check out our
Fish Tycoon Guides Section, where there are a lot of helpful posts.
The strategy you are using works well, as long as you have the Twin-Fin and the Silky in each body type.
