Okay... Time To Fess Up... :)

[Matt75]

So...mine are very very recent.
 
After the slight debacle of finding out the catfish being referred to weren't bronze ones but hiding out plecos (one a good 8 inch common in a 125l tank). Then finding the tank already drained and the contents in a kiddies "my first aquarium" not ready for bagging like I'd asked (3 glass catfish, 3 bronze cats, 2 neon tetra, 2 other tetra I've not idented yet, 5 inch suspected sailfin plec, 8 inch common plec) such that the plec took up a whole corner on its own. And then having to go home and rinse out the gravel (like it or not - the remaining water was black and very disturbed). Before a rapid refill / dechlorine / heat / insert fish.
 
There's also cleaning the decorations in tap water as well during that process.
 
And I didn't really understand cycling - we'd taken advice from a well presented but ultimately limited store on how to setup a tank. To the extent I had to loudly assert that a 25% water change every week was a good thing. More than once.
 
So now I'm fish in cycling and looking at them every day hoping they all make it !

 

[Nik00117]

When I was 13 I was doing a water change, my buddy came over and I went to go meet him something was on the TV that was pretty cool...My siphon was running this whole time...When I came back I have about 1/4 of inch of water left with a ton of fish flopping around.

 

[Supraman]

I listened to the pet store and didn't cycle my tank properly, also when I was 6 I kept a beta in small glass bowl

 

[r.w.girard]

Completely off topic but, excuse me, eating horse, knowingly or unknowingly, has no bearing on the decency of anyone.  There is nothing wrong with eating horse. Nothing.  Tattooing fish is a different story.  They really should not be compared.

 

[McCool]

Completely off topic but, excuse me, eating horse, knowingly or unknowingly, has no bearing on the decency of anyone.  There is nothing wrong with eating horse. Nothing.  Tattooing fish is a different story.  They really should not be compared.

I could start a pretty big argument on this, but I won't, as I know the whole horse slaughter thing varies depending on the county you live in.

 

[laurac94]

Once got 2 killifish which lasted about 2 weeks before jumping out of the tank through the tiniest hole possible only to find my dog having a good time licking them after they had dried up overnight S 2 different occasions too but I didn't know where they were jumping from..found it was the hole my wires go out of BAD FISH!

 

[fluttermoth]

I've never done anything really bad 

 
Of course, I've done all the stupid things;
 
forgot to switch a heater off once and was refilling the tank when I noticed it smoking, so I tipped a bucket of cold water on it. That went well, as you can imagine!
 
trying to fix a rattling external at the same time I was refilling another tank with a hose and forgot about and it flooded the floor.
 
dropped the head of one of my APS externals and snapped the UV bulb and glass sleeve off their bases (still haven't got them out so I can replace them!)
 
oh, and I've syphoned up the occasional fish; once a weather loach that I didn't notice until I was tipping the water down the toilet. It takes a very long time to net a weather loach out of toilet, I can tell you! Took about two hours, and it was a shared house, so I wasn't very popular!
 
I suppose my early tanks weren't cycled in the modern sense, but they were always very well planted and had fish food added for two weeks before stocking very lightly; I never lost a fish.
 
But I've been lucky enough never to have been taken in by an LFS and have never bought a fish without researching it first; even if it was in very old library books that reckoned oscars grew to six inches!

 

[This Old Spouse]

I'm absolutely paranoid about sucking up a fish while doing W/Cs. Sometimes I'll stare into the bucket for a full minute before I dump it down the sink!

 

[DANGI3L]

My first tank was a 14 litre with a common and fantail goldfish, at least it had a filter
I also mis calculated and massively overdosed on a formaldehyde treatment for ich turns out the fish didn't have ich at all and was very unhappy in the water!

 

[ReddSamurai]

i like this post very useful.   but so far i havnt done anything drastically wrong but ive heard stories as i work in a pet shop...selling fish for 5 years so far
and i only just got my first tank 4 months ago and the worst mistake i made was not soaking the bogwood long enough. 
 
and all that happened was my tank got tangoed and even today there is still a subtle hint of orange tan from the wood.
but i cant complain as its harmless too the fish...but it did me i couldnt see anything

 

[CoryLover95]

Of course, besides plopping 20 fish in an uncycled (except with some uber-expensive, ineffective bottled bacteria) I made a few bettas go through horror.  When I was about 7, my parents bought my sister and me each a bowl with a male betta in it.  (No filter, heater, etc, just a plant and some gravel.)  Surprisingly, they both lived for over 2 years, but were sluggish and not exhibiting "betta glory".  Many years later, I got a 1-quart setup with another poor betta, which died after a few months.  This put me off the hobby for a while.  ("I can't raise anything...they all die.  What's the use?")  Later, in another determined attempt, I got a 1-gallon with filter - no heater, not cycled, in which 2 more unhappy fish lived their brief 1-year lifespans.  FINALLY I am now at a suitable 2.5 gallon betta tank with filter & heater - cycled, and a 37-gallon (see the first sentence )

 

[Renahastetras]

thank you for sharing

 

[Noahsfish]

Hmmm...I once added 6 cardinal tetras before acclimating them and they all died within an hour...

Probably the worst and most akward situation with fish has to be a few years back when my sleeve caught on one of the plastic betta cups and sent glass and betta flying on the ground . I ended up not having to pay for it, I've never gone back since...

Sorry I meant glass betta cup.

 

[SamB]

bought "glass/ghost shrimp" from a LFS, turned out to be red clawed macros. yummy.

 
Definitely happened with mine and my girlfriends 10 gallon community - the "ghost shrimp" ate 6 of our neon tetras!! D:
 
Then, after restocking etc we had a big algae bloom. Not knowing what to do about that, we took everything out and scrubbed it. Like. SCRUBBED it.  We looked up how to "clean" the fish, and bathed them in methylene blue. where they all died a very sudden and quick death, besides our betas and 2 false julli cories. It was a tragic night. We were running around in disbelief trying to save everyone!

 

[JBlacksmith]

I know nobody has added anything in a while, but I thought I'd add my confession! My very first fish was a goldfish who lived in a ten gallon with another goldfish, uncycled, and no filter. We would clean the tank only when seeing the fish got hard and we would just scoop them into a tap water filled bowl. The tank was cleaned with hot water and windex which was then rinsed off with more hot water Oh how much I have learned since then. . . haha