What is your worst fishkeeping mistake?


This thread is for the sole purpose of sharing your worst mistakes and ideas you have done. I'm sure most of us have done something we ended up regretting. And we can learn from each others mistakes. What's your story?


Once when I were 5 I had a male Guppy and when he had Fin rot I put Mela fix directly on his tail.... He died shortly after. :'(


Most of my mistakes have been stocking related, and mostly with fish too big for my aquariums. It's a shame that we/I only learn to research fish before buying them after a few losses.

I'm surprised at my lack of calamities overall, though. I'm a magnetic for accidents and mistakes lol.


I treated a saltwater fish disease with a fresh water dip. It was extremely effective the first few times. Then I accidently did one without water conditioner...... Chlorine burn killed it....


Back when I had a saltwater reef, I used a blue damsel to establish the reef for several months. Then, not even thinking about how he probably now considered himself King of the Reef (damsels can be aggressively territorial once they stake a claim), I added a bunch of very expensive new fish to my established reef. The damsel murdered about $150 worth of them the first day, and then I had to chase him for 2 hours and take apart entire sections of my carefully established reef to catch him and get him out of the tank! The remaining fish were so stressed that two more died after he was gone.

For freshwater, my biggest mistake was 20 years or so ago when I got my very first 5 gallon tank, didn't bother to read up on ANYTHING, and just set it up and immediately stocked it with 8 neon tetras, 5 harlequin rasboras, 5 male guppies, a clown loach and some kind of silver catfish (not a cory) with black spots. Whatever didn't die in the ammonia spike was quickly eaten by the catfish, but the tank was so cloudy I didn't know this until the cloudiness cleared and only a fat catfish and a traumatized clown loach remained.


Putting an untested glass heater in a tank & killing the stock.


impulse buys. 'nuff said. They're ALWAYS a bad idea! a close second is leaving a siphoning tank unattended. fortunately, I only lost an extra gallon.


I'd have to say there were many bumbles over the years...all due to pure ignorance!

Let's see.....
Keeping 3 goldfish won at the county fair in a small bowl, maybe 1/2 gallon of water. No filter, no air, and too much food. At 10, if not younger, had no idea why goldfish had such a short life and never got very big

Who needs a test kit when setting up a new tank when you have your eyes and nose. HAH.

Purchasing a brand new 90G tank when I got a divorce. Still didn't know about the nitrogen cycle. Fill 'er up and drop in the fish. Right?

What do you mean I cannot keep goldfish, mollies and rams in the same tank???

Rescuing fish with EVERY opportunity. Bring 'em home. Heal their diseases. Bring them back to health. But when it was time to rehome them, I grew attached to their fight for life, unwillingness to give up under some conditions that I am shocked they survived!

But seriously.....experience is the best teacher. I am sorry for the loss of life along my road of understanding.


A long time ago(way before FL)...we had ADFs......was in a hurry ...and was changing their water......I never added dechlorinator......lets just say it was horrible!!!!!!


I could tell you what my sister's worse mistake that she did with my fish tank growing up. She thought my fish were cold so she turned the heater up in my tank. I came home and all my fish were literally cooked.


Walked away from my tank while using the sink python. I got sidetracked by something shiny, and didn't notice that the sink plug thingy was in. I had a flood in the kitchen. Water spilled onto the counter, onto the floor, into all the drawers, down into the laundry room and my room, and out the back door. I'm lucky we have Pergo floors, but in my infinite wisdom had not bought a mop yet. That was a fun day. I'm guessing about 20 gallons since I was doing a big water change, and I think the sink probably holds 5.


Let's see..........

Keeping a goldfish in a bowl

Keeping 5 goldfish in a 10 gallon tank and only changing the water like once a month >

Stocking a 7-gallon tank with 1 betta, 6 dwarf cories, and 5 ember tetras :-[

Changing the heater in my DP's tank for no particular reason. (the poor thing died of shock almost immediately, currently running the tank with no fish for a week and am going to try again, but be EXTRA careful.)

Sadly, I've made A LOT of terrible mistakes.


10 fish in a 10G tank on day one.

Luckily I found FL 2 days later and have been very successful since.

My only other mistake since joining this site was from being a bit too cocky and buying a RTS thinking I would most definitely have a larger tank before it grew too big to be a problem. After about a month she turned incredibly agressive. She hated my DG for some reason and almost killed him. I had to donate her back to PetCo about a week ago. Broke my heart, but the tank is very peaceful now. Seeing her everyday, I didn't even realize how big she had grown in just over a month until I compared her to a young RTS in the store. She pretty much tripled in size in the time I had her.

fresh water

years ago, washing a used tank out with dish soap, never could get rid of those bubbles on the surface of the water :;madsmiley


years ago, washing a used tank out with dish soap, never could get rid of those bubbles on the surface of the water :;madsmiley


Ya so once I was doing an entire tank clean and water change and had put all my fish into one huge bag...I had a big spiny pleco, I think you all know where this is going . End of day no fish died directly from the incident, luckliy I got them into the bath tub fast enough with the spare siphoned tank water


A long time ago(way before FL)...we had ADFs......was in a hurry ...and was changing their water......I never added dechlorinator......lets just say it was horrible!!!!!!

Mine, exactly I learned to never do a water change when you don't have enough time. (and when in doubt, water conditioner out! >.<)


First tank ever set up, no research was done. Set it up and threw a betta in it. Poor guy didn't last the night


I didn't put a lid on the acclimating bowl while I was acclimating a rare trio of Apistogramma Trifasciatas yesterday and the male jumped out. He died just now. I'm going to put a lid on all bowls that I use to acclimate from now on.

Similar Aquarium Threads


Random Great Thread

Latest Aquarium Threads

Top Bottom