takes a long time to develope but basically it's when the blood cells become inactive due to high nitrate levels. It robs them of their ability to carry oxygen throughout the body. The fish become lethargic, and in low oxygen environments can die. Regular water changes, a good current, and an air bubler should ensure that your cats don't get it. In later stages I have found that the swim bladder will also stop working properly and the fish will actually float instead of sinking. I let my big boy's tank go for too long, and he got brown blood. He was floating. I did several water changes over a few days. It seemed to work the trick, but ultimately that coupled with too small of filtration led to me needing to upgrade my filter system. Alls fine now, but I almost lost him. He wouldn't eat, he had slow gill movement, and he started loosing the color of his skin as well. Now he's healthier than ever. My bi weekly water changes, upgraded filtration, and reduced feeding schedule have ensured that he will be with me for a long time. Do you think one of your cats might have this? Mine basically outgrew his filtration, and needed more frequent water changes as I hadn't been testing his water as usual.
