Giant flying fish (It's not as weird as it sounds)

I am suggesting a giant flying creature that looks like a fish, please put ideas for it's name in the comments, this creature would spawn as a tiny, gray, bat-like creature which can spawn in any overworld location with trees or dripstone, but the chance will be fairly low, but still high enough that most players will get used to seeing it The player will have to tame it using a diamond, this will make it start following the player and diamonds will start growing on its body, after 1 in-game day it is almost entirely covered with diamonds and will begin to look for somewhere to hang upside-down, this space will have to be at least 30 by 30 by 50 blocks in size, in a location like this it will become completely covered with diamonds so that it is in a diamond cocoon, where it will spend the following 2 days growing into a 45 block long fish, once it has grown to this size 10 stacks of diamonds will fall to the ground as its cocoon breaks and it flies into the sky, staying near the player, where it will spend the next 4 days growing until its size has doubled and it is fully matured. Now the player will be able to breed it using diamond blocks, which won't be too difficult to get, because diamond ore will now grow on its back for the player to mine, it will also be ridable and it will be quick, and it will shoot fireballs at anything that attacks the player, and the player will be able to build structures on its back, meaning that now your pet can also be your base.