What's the biggest mistake you've ever made?

Back when I first started keeping fish last summer, I made many, many mistakes. The first two are ones that many people make--buying fish without researching, and putting them in a non-cycled tank. I had six guppies in a 5 gallon hex. I did research the day after setting up the tank and learned a lot about cycling, but still did not realised how overstocked it was. I didn't do anything at that point. The ammonia jumped to dangerous levels, of course (hey! at least I was testing the water, right?). After a couple weeks, the ammonia levels began to lower. Another week or so and the cycle was nearing its end. I had lost a couple guppies and replaced them. After another week or so, the ammonia was nearly zero and all the fish seemed to be doing great and were very active. And then I did a water change one morning. By that night, I had lost two guppies. By the next morning, I only had one left. I was puzzled as to why they died. I had done everything right with the water change. I had remembered to add water conditioner. After a few weeks, I realised what I had done wrong. The water I had added was very cold water, and the water change was about 50%.

I still have that one guppy that survived. She was one of the original guppies I bought. (I still have six guppies in that 5 gallon hex, but they are six juvenile males that get water changes, usually more than one, weekly. And I am moving most of them out of there in a couple days.) I am still paranoid when I do water changes. I have a digital thermometer that I use to check the temperature of the water I am adding and try to make it as close to the tank water as possible. I have not had a repeat of that disaster.
 
I avoided major mistakes by watching my wife make them. She was the original family fishkeeper. She used to change the water maybe every 6 weeks, but would change out 100%, netting out the fish and removing everything from the tank and scrubbing with a bleach solution.
Fortunately she left the biowheel alone and the fish somehow survived the regimen. After a while she ended up with a chronic BBA outbreak. A new fish with ich eventually wiped out the entire tank and she gave up the hobby.
 
During an icestorm last winter in upstate New York, the power went out and the hot water in the entire town also shut off. My tank from 80 degrees to 50 in about an hour. I was totally unprepared, panicking, and although I eventually got the situation under control, I lost a couple of small fish from the trauma. Luckily they were still fairly new and I wasn't attached to them yet.

Wasn't really a mistake on my part, but next time I will be more prepared.
 
I had a brake cleaning compound spayed on my upper arm at work, and promptly forgot about it. Washed my hands well after work, but I don't have a dirty job, and forgot about the chemicals on my skin. After work I reached right into a 45 g aquarium to adjust a piece of driftwood. You know the rest. Its the worst mistake in 15+ years in the hobby.
 
my original stocking, and buying a clown knife. because now i have to find them all a home.
 
i've been keeping fish off and on for 40 years and my worst mistake was just recently. i use a python to drain and fill my tanks, always try to match the temps before filling but one time i didnt check it close enough and ended up with my 75 gallon at 90+ degrees.. immediatly started draing and pouring in buckets of cold water... i got lucky and didnt lose a fish but i check the temps a lot more carefully now
 
listened to 4 different lfs on how to cycle a tank,.. when i first started, then after almost killing the fish i did what felt right and then found out it was right,.. so........:silly:
 
I am currently treating a case if ich and my new canister filter showed up.

I left my old filter in and installed the canister. I positioned the spraybar so it would spray onto the heater. I figured it would help move the heated water around.

I had my tank set at 86 degrees to help with the ich. My fish have been fine with it (dwarf gourami, platy, molly, rummy nose tetras).

The next day my tank was 90 degrees. The spraybar shooting water onto the heater must have screwed up the thermostat in the heater. Luckily all of the fish were fine and swimming normally. I rearranged the spraybar so it no longer sprays the heater and it's back to 86 (and the fish still have spots....).
 
Quite a number of years ago we lost a blue eyed plecostamus - about 12-14"....my husband thought he could flush him down the toilet, and he did! Needless to say the next day he was busy taking the toilet right off the floor and snaking out the plumbing to retrieve a bloated & very stuck dead pleco! :o Any large fishes now get a "burial by dumpster" instead of "burial by sea".

:rofl: Had this happen with a rather large goldfish. Had the plumber out the next day oops :lipssealedsmilie:

My biggest mistake had to have been thinking I could just buy fish and stick them in a tank w/water. Just tap water mind you, I had no clue about dechlorinators or anything. So yeah I went out and got me a nice 30g, overstocked the p#$$ out of it, and killed my $50 investment of fish. The ghost shrimp survived though :thm:

The next biggest would have to be not having a generator and being out of power for 5 days. Nor did I do any research like floating a bag of hot water, wrapping the tank to keep the heat in, do not feed etc. I lost all my bloody fish except a cory cat who is still with us today.

Heck I still make mistakes, most of the time it involves not thinking before I act. :headshake2:
 
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