My goldfish suddenly died?

Alright, so here goes.

I had two goldfish in a 55 gallon tank. One's a fantail, the other was a black moor. I had them both for three months and neither showed any signs of sickness, they were both perfect. Then all of a sudden, last night, the black moor started acting weird and staying near the top of the tank and swimming behind the tank filter. I soon discovered he was like this because there was something wrong with his swim bladder and he couldn't keep himself up and control where he went.

I didn't feed the fish that night and was planning to treat him for swim bladder disease so I could get him back to normal. But within the course of a night, he lost all color, his fins became ragged, and he died. His find were never clamped and he seemed normal otherwise, so I don't think anything else could have killed him, especially since the other fish is unaffected. I've never had this happen before and I'm rather upset.

Here are the details of my setup:

55 gallon tank, fully cycled
Two goldfish, both less than two inches in length
Two filters rated for 60 gallon tanks
No ammonia, nitrites, or nitrates
pH at 7.1 (normal for my water)

There was literally nothing wrong, his fins weren't even clamped, even as he died, so I don't know why this fish up and died like this. Anyone have any ideas?

 

I suggest that it was lack of oxygen, as goldfish tend to consume a lot, and it sounds like it from the description you gave.

 

Same happened to my beautiful Cory cat 2 days ago, no sign of illness and bam! One day I find him dead. I was so so upset. I thought maybe it was a parasite of some sort so I put some paraguard in the tank for a few days, everything seems alright now.

Keep me updated.

 

Fish diseases are so hard. :-(

On another forum, I have seen people recommend a round of PrazI for every new goldfish, on the assumption that virtually all goldfish have gill flukes. I'm not very experienced with this, but the mention of swimming by the filter made me think of it.

 

Oh ok!

Is it okay if the other guppies and platies fast as well? I don't have a hospital tank with a heater.

 

I don't think it's lack of oxygen... I have two filters and one air pump agitating the surface of the tank pretty well. Like, the whole surface is always moving. Is that not enough?

 

AnneRose, I'm going to go get some ParaGuard at my local pet store later and see if that helps!

 

Update: now the other fish is showing the same exact symptoms of the first one and is probably going to die too. It's obviously contagious but I have NO clue what it is because it doesn't sound like any fish disease the Internet has encountered. Anyone have any tips for cleaning the tank once everyone is dead so that I can buy new fish without them catching this?