What mistakes have u made in fish keeping?

[ShadyFish04]

Hey you guys! Ive been thinking about all the mistakes I have made or have seen people around me make when it comes to fish keeping. I think we can all learn from each other's mistakes and hopefully not repeat the same mistakes as others One big mistake I have made in the years of owning fish was having tanks too small for betta fish. I had not done proper research on betta fish tank size and actually had a better like in a tank slightly smaller than a gallon :/ horrible, i know. Id love to hear some of your mistakes

 

[V227]

Hello Shady
Over my three decades of fish keeping, I've been very fortunate not to have had many outbreaks of disease. That's why an outbreak of Oodinium took me by complete surprise.
The disease was introduced into the tank by a new fish that had been Quarantined; apparently not long enough.
The fish had been sick a couple of days before the tell tale symptoms of Velvet were evident. Here's the huge mistake I made. I was a little over confident in my abilities to cure the fish with a non med method. A few days later the die off began, and the disease had been spread to my juvenile grow out tank.
Oodinium is an awful parasite. Much worse than Ick. I witnessed the skin literally peel off some of my most prized fish, two of which, I'd had for thirteen years.
In summary; I nuked both tanks with a copper based med. I lost 90% of my display tank fish, but saved 90% of the juvenile fish in the reserve tank. Had I medicated at the first indication of disease I'm confident there would have been a much more positive outcome. I know med-less cures are popular and often recommended. IMO Prevention is the best medicine, but if disease strikes, correctly diagnose, then use the appropriate medication.

 

[MattS99]

I had a tank with only a school of lemon tetras. On a really, uncommonly hot day in January, I left the heater in the tank. With the windows shut and extra insulation in the house I inadvertently fried every single one to death. Came home from school to an entire dead school in the tank, didn't know why. Then I felt the side of the tank... It was well over 100F. I wish I still remembered the actual temperature it hit.