My little Azura didn't seem to be eating well over the weekend. I did a 100% water change (her tank is 1.75 gal.) on Monday night, which usually makes her perk right up. Instead, I dropped her back in (into water which was dechlorinated, the same temperature it had been) and within minutes she turned a horrible ashy color with stress bars just popping off her. Now that I think of it, I probably should have taken her right back out and popped her in a cup or something, but I was so confused I didn't think of it at the time
Besides, it normally took her a few minutes to adjust to new water.
Anyway, I just kept checking on her, and she had enough color back when I went back to bed that I thought she was okay. Her fins were a tiny bit clamped but I thought that was her recovering.
She looked almost normal Tuesday morning, then I came back Tuesday night and she was lying dead on the gravel, almost white. I don't have any idea what happened.
I'm racking my brains to think what went wrong. I am absolutely sure that I did the water change exactly the same way as usual. The temperature in her tank was something like 77-80 the whole time and I know she'd been through much worse (before I got a heater). I think she must have been sicker than I thought over the weekend, but she had no symptoms other than being a very little bit pale and kind of picky about her food.
Does anyone have any ideas? What she might have been ill of and how I could have cured it? Obviously it's too late to save her, but if something like this happens again, I want to know if there's something I can do about it.