Tech, again please read the posts that are posted.
Cold water fish require more oxygen in their water more so than tropical fish.
Gold fish produce a lot of waste that will cause a lot of problems in the long run. causing you to do more water changes in the long run, a couple a week.
Also goldfish will easily out grow a 10 gallon and require a larger tank in the size of 55 gallons and up. Actually, goldfish are more work than the live bearers, in upkeep. And plus, once the goldfish will get to a certain size.. guppies=lunch.
So again, please do some research and reading, check out the links that i posted before.