Hi. So I have two goldfish in a ten gallon tank (I know that is too small but we are moving so our larger tank is sitting idly by for now). They have been in this tank for about 3 weeks, and I changed their water once a week(70%). Two days ago, I saw that my black moor has red bruising underneath, between his fins. It looks like internal bleeding or something. Since noticing it, I changed their water again (70%), and have cut back on feeding them. The other regular feeder fish seems to be fine, but the black moore is becoming lethargic. I checked the ammonia levels today (because pictures of ammonia poisoning seemed to the closest to his condition)and they were at zero (not test strips but actual test kit). His fins aren't rotting, and I only really see red on his chest area, his gills seem a little pale too. He isn't getting any better, and I might argue that he is getting worse because he is starting to hang out at the bottom of the tank. He swims up for food, but otherwise he's been hanging out at the bottom all day. He also seems to be unable to control his balance. he starts floating upside down kind of, until he gets back to his regular position. I don't know what to do. this is my first time owning goldfish and I am terrified. Any advice would help. oh! He also seems to be constipated because his poop is white and stringy.