Worst thing that ever happened in your tank?

I’d have to say when I adding in a pretty badly attacked black knife eel as a friend was tearing down their tank, only to notice a day or two later that it completely killed all of my other community fish in the tank (not sure if it was an attack feast, or if it was super hungry, or what). Kinda sucked the most as doing a favor tended to make me restart my whole tank.

Probably the worst thing for me was a heater malfunctioning and basically shocking or overheating my fish while I was sleeping.

Definitely not a fun time getting them all out while also getting shocked slightly until I found the piece of equipment that caused it.

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So many early mistakes come to mind, not really sure. A lot of my fish died when I was a beginner.

We had a 75 gallon tank when I was a kid, so to me the worst thing that happened was when the larger fish would eat the babies right in front of me.

I went on a vacation. When I came back after 2 weeks, all of my goldfish died. I had a dozen goldfish. When I was on a vacation, there was a power outage for 24 hours which led to disturbances in the ecosystem of the tank.

When I was a kid, we had a huge tank. One morning I woke up & there was water on the floor. The tank had a small crack, still don't know what happened to this day. We lost most of our fish. The upside was we were going on vacation that morning so my dad was home to help clean it up.

Quote from popopdc

So many early mistakes come to mind, not really sure. A lot of my fish died when I was a beginner.

Mine was when s lot of fishes died as a result of polluted water. I felt it for days and couldn't even focus on eating for a while.

Quote from popopdc

So many early mistakes come to mind, not really sure. A lot of my fish died when I was a beginner.

I have had so many other fish pond disasters but it's definitely cannibalism that's the most which took me a while to control. It's one of the disadvantages of having your pond overcrowded.

A bacteria infection called Aeromonasinfection was what hit my fishes one time in the past. I kept treating it and it kept on coming back. It killed at least 3 of my fishes before I was able to fix it.

It wasn't something that happened to only me, but it was something that happened when I was younger and living at home with my parents. We had a huge tank that would stand on the floor, we had it placed in front of the window in the back room of the house. It was full and we had plenty of fish in there and we never seemed to have any issues with it. We made sure the seals were secured and redone before we filled the tank and for quite a while the tank was fine. It was one morning, and I remember this like it was yesterday, it was a Sunday morning, and I woke up to my Mum sounding a bit angry, curious as to what had happened, I went downstairs and the tank had cracked down the front and there was water all over the back-room floor, we lost some fish that got caught within the crack and some survived. After that my parents never got another tank and we moved the fish that survived into the pond outside.

Some guests who had come visiting our home had put some bread crumbs as feed for the fishes and most of my fishes were dead and floating with their stomachs bloated after feeding on it. I still cannot figure out whether it was a consequence of ignorance or a purposely done act.

Quote from Betta

Some guests who had come visiting our home had put some bread crumbs as feed for the fishes and most of my fishes were dead and floating with their stomachs bloated after feeding on it. I still cannot figure out whether it was a consequence of ignorance or a purposely done act.

That's awful really this is precisely the reason why I do not let any other person except me to feed my fishes.

I learnt a really hard lesson after that. I do not allow anyone without supervision to go near my tank.