Goldfish mysterious death..?

[John Simple]

So i had this big goldfish in a 60 gallon tank, he was very healthy. My tank looked cloudy so i did a 75% water change. When i put new treated water in blood started to spurt of the goldfish gills, really a lot of blood. He was still moving a little bit but quickly he floated dead to the top.

Why did this happen was something bad in my water please help because i dont want this to happen again,

 

[Rbishop]

What was your regular tank water change routine? Tank parameters from a good liquid test kit?

 

[FreshyFresh]

Oh man. Sounds absolutely horrifying. Like rb said, do you know what your water parameters were, or are at now? Did you do regular weekly water changes?