about a year ago, my sisters got a 10 gallon tank and put 5 goldfish in it. Of course, they didnt know about cycling a tank. So They always did 100 percent water changes. And lately I've been changing their water ( about 30 percent ) Just so they could have some nice water before i switched it with an already established tank. I never checked water perameters, because I did so frequent water changes, I ussumed there would be nothing to see. But In todays water change, I decided to check on Nitrates Because I got suspicious. Sure enough, there was 5 ppm Nitrates. I Guess I did a fish in cycle lol. I am suprised Because I've never actually cycled an aquarium before, and now i've done it by mistake.