My fish die one by one

[Lynx]

2 of my fish died a short while ago. I was left with 3. I moved them to a QT tank. Treated with levamisole, prazi and antibiotics.
But they all died one by one.
They are all dead.

And it was a very sudden death. These fish looked absolutely normal just a few hours ago. Suddenly they fell to the ground and died.

I'm speechless. I have no idea what is going on.

[Lynx]

I also examined one of the dead bodies under the microscope and found literally nothing.

[Second Hand Pat]

Hi Lynx, did you treat them with all the meds at the same time in the 10 gallon QT?
Pat

[Lynx]

No, the meds were being given separately and in the big tank.

Now I'm left with the 3 fish I bought recently. They are currently in a 30 gallon tank. They seem to be doing fine (except for white poop, I'm gonna give them metro I think) but I would really like to find out what happened to these poor poor fish who died in order to prevent causing such a mess in the future again.

[Second Hand Pat]

May I ask what you were treating for? How long were you resting the fish between meds? Do you have any pictures?
Pat

[Lynx]

i'M SORRY ITS UPSIDE DOWN AND HORRIBLE QUALITY BUT IM SHAKING LOOK WHAT IS HAPPENING RIGHT NOW THESE FISH WERE IN SEPARATE ****ING TANKS.

It's pretty much over.

https://youtu.be/1W70sVc8bxo

[Lynx]

This is what happened to other fish all was well then suddenly they start rolling like that and minutes later they are dead.

[Second Hand Pat]

Lynx, I have no clue what is happening. Could you please measure ammonia, nitrites, nitrates and ph? Is there any filtration on the tank?
Pat

[Lynx]

No bio active filter in the QT because instruction on my meds say I should unplug any filters. I changed their water like 20 hours ago and they were receiving no food.

[Second Hand Pat]

That is really bad advice and I suspect the fish reacting to measurable ammonia and nitrite. Do a 100% water change NOW or as big as you can.
Pat

[Lynx]

doing the wc atm but i lost hope it will help. other fish are showing no symptoms but if all goes the same as with the small fish i had they will get symptoms all of a sudden then die within an hour like what is even going on...

[Second Hand Pat]

Please post back how the fish are after the water change Lynx.
Pat

[LizStreithorst]

Lynx are you sure the instructions didn't say to remove carbon filtration and not to turn the filter off. As pat requested, please test ammonia, nitrate, nitrite, and post a pic when you calm down.

[Lynx]

GUYS

You're not gonna believe it.
I don't believe it.

While doing the water change I dumped the poor guy who was on the verge of death into high concentration of nitrofurazone and furazolidone like doing whatever was there left to do and AFTER LIKE 30 SECONDS NO JOKE he was back to normal swimming straight like what the hell...

While the other baby fish in the other tank were dying from the same thing I changed their water to 90% fresh and they died anyway in a matter of an hour since the WC.

I'm gonna do some tests I just gotta calm down.

https://youtu.be/VaNzLXoLxjQ

[Lynx]

I really hope these fish will not die. Like I have no idea what is this disease.