The 21 perfect fish aren't really an official goal of the game, so you won't be notified when you breed any of them.
I can't explain why the seahorse tip isn't showing up - there are supposed to be 40 tips. After all this buildup, it seems a little anticlimactic - but this is what that tip says, "The seahorse does more than just look pretty..." I guess that's Arthur's and Carla's way of reassuring people that it really does something!
