Hello its me again. I just noticed something on one of my goldfish that is rather alarming. One of his gills has turned bright red! I am the one who posted "my new goldfish(pictures included)" recently. After I got all that information I decided to bring them home and move them into a nice big tank right away. I don't have much money so I got them a 10 gallon tank, since its the cheapest, they will only be in it until the end of the year so don't get too worried, and they are still very small. I'm asking for a large tank for chirstmas. I have everything sitting here ready to go, and I was going to move them into the bigger tank when I got back to school tomorrow then I saw this. Does anyone know what it is? I know the tempurature is fine but I haven't tested the water yet, I am going to buy testing supplies tomorrow, what should I test for? I also have a other animals in my room (betta, guinea pig, leopard gecko, yeah i'm nuts) could they have gotten something from one of them? Should i seperate the two goldfish until it clears up? I don't want anything to happen to them, I know I didn't get off on the right foot, but now that I know what I should be doing I want to do everything right, thanks in advance for any help.
**edit** I just noticed they both have it
also I have amquel plus, accu clear, and stress coat, would any of these help?