Wow! That’s a huge collection already! A shiny Mewtwo even, that’s amazing! I am planning to breed for a shiny Fennekin as well.
Do you already have a shiny Clauncher? I could possibly help you with one if you’d like. I’m not sure whether I have one in my box or traded them all, but they’re not hard to get in my X version. I also got many Horsea in both X and Y from chain fishing Skrelp and Clauncher.
Welcome to PokeBeach! Another Casual VG Player (I am too)! Did you beat X/Y? I read you're a shiny hunter. What did you get so far? My favourites are my shiny Greninja and Aegislash.