Unsure about gender of current fish

[SharpieItBlack]

So I want to get a second goldfish in the next few months. But I'm unsure of the sex of my current fish. I named it Jack and assumed it male, because I just wanted to name it after my favorite video game character. But I'm actually unsure.

At the pet store it didn't have them separated male or female. They just had the one tank for the Calico Telescope Eyed Goldfish. When I get the second fish, I don't want to end up with more fish (don't have the space or money for anything bigger than a 55 gallon).
What are some characteristics of the genders of fish to see? I'll include pictures if I need to.

 

[jlk]

Do you have any idea how old your fish is? Goldies can be difficult to sex even when sexually mature. Males when well conditioned will develop breeding tubercles on their gill plates and pectoral fins. They look like little white or colored bumps/bubbles. Males will have a more streamline firm body and a concave vent. Females will have a round, soft, lopsided appearance when viewed from above and a convex (protruding) vent. Hope this helps a bit!

 

[SharpieItBlack]

Do you have any idea how old your fish is? Goldies can be difficult to sex even when sexually mature. Males when well conditioned will develop breeding tubercles on their gill plates and pectoral fins. They look like little white or colored bumps/bubbles. Males will have a more streamline firm body and a concave vent. Females will have a round, soft, lopsided appearance when viewed from above and a convex (protruding) vent. Hope this helps a bit!

Definitely helped, thank you! Well I bought the fish back in late august early September last year, and I am guessing it is only that old? Was a tiny fish when I bought him, now not so much

 

[jlk]

This link will help as well. Pictures give a much better visual idea than trying to explain the differences in words.

Sexing Goldfish