The goldfish pics are (Lt to Rt) - Pearlscale, Mixed Ranchu/Fantail?, & really nice Ranchu (with nice wen).
All 3 are relatively weak swimmers, and all (esp. the pearlscale) demand good water conditions.
From what I read, the world record size for a fancy goldfish (according to his owner - a breeder in the far East) is 12-14". He is Bruce (named after Bruce Lee) & a Ryukin. However, fancies typically only grow to 6-8".
The size is deceptive. Fish make waste based on body mass. Most tropicals are thin, so don't have much mass. A chubby goldfish has girth as well as height. A 1" goldfish can easily weigh 10x more than a 1" tropical. The size increases exponentially. A 2" goldfish is about 8x heavier than the 1" baby, and a 3" might be 27x that. It is easy for growing goldfish to outstrip their tank.
Anyway, you tank has a surface area of ~175 sq in. That is even a bit smaller than the surface area of a standard 10 gal. Based on that alone, I would discourage you from keeping goldfish in it. If you really want to try it, I would suggest no more than 2 fancies, preferably smaller specimens and hardier variety (metallic fantails or moors). You can be successful provided that you are diligent with water changes & cleaning, and keep close monitoring on the tank so you know when the tank's capacity is being exceeded. <And no, I would not suggest "cheating" on pwc's with goldfish in a small setup (like a previous post).> I would guess that a pair of 3" fancies would be near or over the max carrying capacity of that tank. So I would also expect a backup plan for when the fish get big - ie a bigger tank, pond, etc. <For me, goldies are pets & family. They are not disposible.> Remember that goldfish can live over 10 years, so please plan accordingly.