Mistakes Made/lessons Learned

[RobRocksFishTank]

Most of us have made some mistakes for a variety of reasons as we learned how to properly take care of our charges. Be it misinformation, misconceptions, or plain old mistakes. Some were costly, some messy, some just made us ask ourselves, "What was I thinking?" I started at day one with my first tank, a used ten gallon that my friend gave me. I put fish in the day it was set-up. That is actually more than one mistake.
 
I think my first really detrimental mistake was bringing home an Electric Catfish from the fish store that I was working at. I had a well established community of a few South American cichlids with some dither fish. I lost half my fish and my favorite fish, a Jack Dempsey that I had trained to jump out of the water to take food out of my fingers, got brain damage as his feeding response just turned off one day. He lived quite a while afterwards, but was never the same after that. BTW, that "training" was another mistake. Do not try that at home.
 
I've got plenty more but will hold them back until you share some of yours.

 

[colleen0309]

I left the top open on my breeding angelfish and they both jumped out in the middle of the night. I lost both of them.

 

[LyraGuppi]

Hmmm...never keep a betta in a bowl. I'd done this too many times, just out of ignorance.
 
Never leave an algae wafer unattended in a betta tank!! Ever! They are monstrous pigs.

 

[Gruntle]

Buying non-aquatic plants from the LFS that were sold as aquatics. I've had them decay fast enough to poison a newly cycled tank and kill most of the fish.
 
Pretty much every mistake I've made so far is related to taking advice from a LFS and not doing my own research.  That and buying pregnant Endlers (although that's a happy mistake and I'm in control of it now).

 

[WILDER]

This is get your hankies out and cry thread.
.
I can only really remember one really heart breaking episode in my fish keeping experience and it was
adding more neon tetra's to my shoal and the new ones had NTD and vertically wiped my whole tank out!
Really up setting and from there I bought an isolation tank that doubled up also into a hospital tank.
 
Counting all the fish after a water change also as I found one dead fish a few days later behind the tank.
It must of jumped out during a water change. Really made me feel guilty for not paying attention.

 

[betta fish]

Not quarantining a Lawnmower blenny before adding it to my lovely established marine tank with two Clownfish that I had for 2 years, they both got brooklynella  and died within 24 hours of first symptoms there was nothing I could do it was so quick, the lawnmower blenny also died as I struggled to get it to eat, I gave up marines after that 

 

[Ch4rlie]

Oh ho!
 
I've made my fair share of mistakes!
 
The one I regret most is, when I was doing salt dips for one of my threadfins to treat for fin rot or something, can't remember exactly, at the time, I mis-measured the salt and dechlorinator by adding far too much.
 
Needless to say, it did not end well for that poor threadfin.
 
Lesson learned was always double and even triple check measurements of anything you add to the tank, especially dechlorinator.

 

[malfunction]

For me it was adding too much medication and poisoning the majority of my breeding stock of rainbowfish. I had forgotten that some meds deoxygenate the water and ended up killing the rainbows. Lesson learned was not to administer meds when tired!

 

[nic1]

Mine was.... Now don't scold me now as I was only a kid and didnt know any better,
Using non aquatic items like those plastic little bins that held bubble gum and other sweetie containers as tank decorations, at the time i couldn't figure out why my Fish were dying. It was only when I managed to wrote out all of them that I emptied the tank and all the so called decorations were like mush to the touch.
#wipe out not wrote!

 

[RobRocksFishTank]

I used to think that fish could not get electrocuted, like a bird on a wire. I found out differently early in my career. I was cleaning a tank and had placed the light strip directly on it so I could see what I was doing and it fell into the tank while I was doing something else, luckily my arm wasn't in it. The fish immediately jumped out of the water. I was able to react quick enough to save everyone.
 
Lesson learned: Be careful with light strips.