HUH???????
Open your eyes!!!! Look at the pictures in my post that's way more than "Small Variation within species", Goldfish have evolved into a different species from carp
Look at again, Here's the bubble eye breed first recognized in the 1920's
Differences between the original carp it evolved from
1) 94 Chromosomes instead of 100
2) Different color, Gold instead of Grey
3) New organ evolved, The Fluid filled sacks (Bubble Eye)which includes new blood vessel supply and regulatory system
4) No dorsal fin
5) 2 Tails instead of one
6) Eyes facing upward instead of on the sides
7) Fewer columns of scales
8) "Egg" shaped body layout instead of "Cigar" shaped
9) No Barbels
10) Bone structure altered
11) Frontal Swim Bladder rounded instead of elongated
12) Different size of other fins
13) Able to survive in captivity
And so much more, That's probably more differences than you can name between Chimps and Humans and that's just the bubble eye breed other breeds of Goldfish also have a wide variety of other evolved features (i.e Lionhead, Pearlscale, Telescope, Pompom, Etc.)
Those aren't just variations of the carp, Those are new features/structures/organs that evolved. You will not find a single one of those traits in a wild carp so it's not just variation within species. We know these features evolved because we have the total historical record of the Goldfish which first came about relatively recently in China in about 1000 A.D..
I guarantee you, If you find someone who didn't know through historical records that Goldfish came from Carp, If you showed them picture of any one of those breeds at the bottom of my post and a picture of a carp they would not only not be able to identify them as being related species but they wouldn't even believe they are in the same family (or "Kind" if you prefer).