One silly and very short filly "fic" wrote on Twitter some days ago: Filly Mermaids are a fishy race, let me say.
Not just for the tail.
My first language is not English as you know, and I would ask some proofreading to fix some raw passages/errors. :)
"The truth about Filly Mermaid"
The Filly Mermaids are, in truth, the pirates of the Filly Caribbean, who stash the treasures raided from the ships they sunk.
Long time ago, Cedric ordered more fifteen magical swords from the Witches, but the ship was sunk by the Mermaids, and the weapons stacked with the rest of the loot in the Treasure Box Castle.
Becouse of this, Cedric became an inventor and built a cool nuclear-powered submarine; then he razed the Mermaid fortress and got back his swords. After the storming of the Glitterina Fortress, a bloody war between Princesses and Mermaids broke out, until the peace treaty held by Princess Sparkle. This event led the foundation of the Academy at the flying island-keep of Funtasia, a year later.