Sudden fish deaths

[Cari]

In the past 24 hrs, 4 fish have died in a tank that I have had for a decade. I'm usually pretty good with catching things before they wreak havoc on my tank. All of the fish look fine, but 3 died sometime last night....and one (my favorite redtail shark) is dying right now. I haven't the slightest idea what is going on, but the poor little guy was fine when I got home from work just after 4pm. When I came back from doing groceries, he was on his side at the top of the tank. When I tried to get him out, he swam away fine. This just occurred a few minutes ago and it's about quarter to 7 here now. I worked all day and nothing happened during that time. All of the fish appear fine. All but that one are swimming around like usual...but so was he just a couple short hours ago.

Does anyone have any ideas what could be going on? I've not changed anything with my tank as of late, so I'm just utterly confused......

 

[Zagz]

Did you test your parameters to make sure nothing went out of whack? Are the fish 10 years old? They could be dying of old age although seems unlikely that they would do it at the same time. Any chance something unexpected could have gotten into the tank? Do you have kids that might have added something to the tank?

Welcome to AA btw. I'm sorry it is under such sad circumstances.

 

[Cari]

Thanks for the welcome.

There are only 2 plecos in the tank that are as old as the tank itself. The rest of the fish have all been in there for at least 8 or 9 months. Everything tested fine, and none of the fish have any lesions or anything of the sort. I used to have a 10 gallon tank that I'd use to quarantine fish that became ill, but it cracked when I moved last year....so I really have nothing to put him in. It just seems so sudden. It's a 55 gallon tank and I've never had problems like this ever. If they looked sick, then I could figure it out. It's the lack of symptoms that is seriously driving me insane.

 

[Zagz]

I understand your frustration, sometimes these things can happen even though we can't explain why. I would do a pwc anyway, it won't hurt and keep an eye on things. Has the shark been eating and pooping? Is his stomach swollen at all? Asking because constipation causing a swim bladder problem came to mind. Grasping at straws here,

 

[Cari]

He hides much of the time, but he looks like he's been eating fine. His shape is normal. He just seems to be struggling to keep going at the moment.... :?

 

[Zagz]

I wish I could offer more help. Like I said I'd do a water change and keep an eye on him.

 

[MarcoDaVinci]

I have experienced sudden and unexplain fish death (neon, pleco, zebras) when my phosphate level was too high, due to unbalanced plant fertilizer.
I would suggest a Nitrate/Nitrite and Phosphate test, it does not hurt.

 

[MarcoDaVinci]

I have no idea how your tank looks like, but here are two ideas

- I have experienced sudden and unexplain fish death (neon, pleco, zebras) when my phosphate level was too high, due to unbalanced plant fertilizer.
I would suggest a Nitrate/Nitrite and Phosphate test, it does not hurt.

- If your thermostat does not regulate right, the temperature can sometimes go very low and very high. I had this problem with an old thermostat once, and the temp was oscillating +-5F around the set point. Also, is the water circulating enough to make sure the temperature is homogeneous ?