Your biggest mistake

  • We are currently upgrading MFK. thanks! -neo
The dog had destroyed the algae scrubber brush. So I used a sponge to clean off some algae. A sponge I forgot I had used to disinfect with bleach a tank a month ago. After an hour, nothing was alive. Fortunately, it was just a guppy/molly community tank which has since been recleaned, firemouths injected, and I threw out that sponge.
 
my biggest mistake was not trying to make the new tank's ph similar to the old tank. the old tank had 6.0 and the new tank had about 7.2. i hope the fish get use to it..
 
doing a WC with the glass heater still turned on.

lucky there were no fish.
 
putting a convict in the same tank as my angel for 20 minutes when i was changing tanks around :( it destroyed my angels fins
 
Trusted the people at the store for info instead of doing my own research. Now I know better . . . even the lfs, which is pretty decent, occasionally makes some dumb mistakes (for example, they have Endler's mislabeled as "Lender's," and literally don't know the difference).

The chain stores, of course, are considerably worse. I started fishkeeping by letting my little girl pick out one betta from Zamzowe's. The employee there assured me that it was one of the only fish that would survive in my house just fine without a heater. Well . . . the poor thing got ich and died before the week was out. Zamzowe's replaced it, hassle-free . . . and that one died three days later. When they offered to replace the second fish, I just gave up and walked out. We didn't try keeping fish again for a couple of years.

Now I know that bettas need room temperatures considerably warmer than the ones at our house (67 during the day in the winter; about 65 at night). How hard would it have been for the employees there to have done that much homework, instead of just offering to keep replacing the fish indefinitely? Grief!
 
Not actually checking to see if my newest knifefish were African, or Brown and trusting the lady at my local pet store. they were African, fortunately after a few weeks with a separator they were fine with my other knifes/bichirs/& placo I was VERY lucky on that one (sigh)
 
I was swapping heaters in my 55 gallon and 29 gallon tanks, I forgot to plug the 29 in and killed a 15 dollar "Rhino" Pleco. I thought it was my africans until I checked the water, 66 degrees lol.
 
Trying to move pimelodus blochii with nets. The pet store used nets, so I thought it would be ok. They must have had some sort of special net(or were lucky). The first almost got stuck, but made it into the aquarium. Like a fool, I tried it with the second one. One of its pectoral fins became tangeled. Had no choice but to cut the net. The piece of net came off in less than a week. Now, I use a small caramel corn bucket with holes in the bottom, when I need to catch them.
 
Putting a rare 10-11 inch True Rio Trombeta Marmorata in a quarantine tank without a top.
Needless to say she jumped and I found her the next morning, still breathing, but she did not make it.
 
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