When I was about 13 years old My first "tank" was not a tank at all. I bought 3 betta frys and kept them seperated in a 3inch x 5inch plastic pen organizer. 1 fry survived long enough to develop colors. Then it jumped out.
Made a few mistakes as a kid, this was probably 18 years ago or so (26 now).
Started off with a 20g, and knew nothing about fish. Didn't overstock it too badly; started off with a couple of angelfish, some neon tetras, some cories, and a couple of those blasted chinese algae eaters (i still hate them till this day). I was smart enough to research the nitrogen cycle though, so my tank was cycled by the time it was stocked.
Then I discovered Petsmart.
They sold me six clown loaches.
Most of the neons died in the following 2 weeks, all the clown loaches got ich and only 3 survived (i still hate myself for that, they still are one of my favourite fish). I ALMOST made the mistake of using a copper containing chemical to treat them, but my LFS had some great employees that steered me in the right direction.
Realised what the problem was, guilted Dad into buying me a 55g for my birthday, promptly rehomed the fish into it (wound up giving the loaches that survived to my LFS).
Had a really strange occurrence with congo tetras though.
Left the remaining neons in the 20g, saw some congo tetras and a GBR at the LFS and bought them, figured they would be fine in the 20g with the neons.
The lights went off that night, and it was a bloodbath.
The seven remaining neons were torn apart by some very vehement congo tetras, and those tetras remained alone with that GBR until we moved away and gave them back to the LFS (we moved from Canada to Australia).
Most people learn once they **** up a few times, but not always, unfortunately.
Saw an ad on a local marketplace while browsing fish and tanks, some lady has had an angelfish in a 5g for its entire life.
It still managed to grow to mostly full size, but damn.
I can't afford to go around rescuing every fish (that damn barramundi is going to be trouble, I can see it now).
First Tank 5 Gallon, started with 2 comet goldfish ( according to my mother, far too young and in the past to remember now)
Afterwards I wanted to try tropical so I got a heater, a red-tail shark and silver shark. I don't remember how the silver fared but the red tail was literally unkillable and my mother resuscitated it after he jumped out. That fish then survived me once overfeeding my mothers fishtank ( because feeding fish is a good thing to do when you are a small young unknowing child ), naturally the ammonia spike killed off the mothers freshly brought discus and the majority of the rest.
Not actually me killing this one, but in the same 3ft of my mothers we had a fire eel, probably 1-2ft in length ate flake too, when moving out of the flat me and mother lived in, my father who was helping move furniture opened the window and the tank heater wasn't on. Sensitive thing keeled over from the sudden temperature change. Not really my dads fault for not knowing about the fish but young me hounded him for over 5 years over that fishes death, I was very attached to my very big, very long leviathan eel even though I had no idea how poor my husbandry for it was.
Somepoint during all of this we brought a bristlenose pleco, I wanted a common pleco because they grew huge but my mother was intelligent enough not to get one. Long story short after another move this fish ended up in my 5gallon after making Chinese algea eater horror stories seem like children's books, it was forgotten about and never actually fed and found as a skeleton several months later.
2nd Fire Eel we brought online because the first 1 had me completely enthralled by them. Only noteable thing of this fish was how little it ever did before dying at the very front of the tank spontaneously in a spasm or fit. It had a weird kinked back from the start we could only assume was from the postage.
3rd and 4th Fire eels from lfs we brought together, because I wanted to breed and raise up fire eels. They did incredibly well in the 3ft, my mother and I argued over food cost vs. underfeeding them and the tanks being too small. We gave them up to the fish shop after they fought and one ended up with a large bite mark in its tail and we couldn't fit them between my mothers 3ft and my 40gallon.
And now in the present day, several years later, I'm looking to buy myself a 9x3x3" fish tank and finally house these things properly, and maybe pick a super red Asian arowana later down the line if things work out, seeing how I finally have my own income from leaving education.
Not quite all 10 gallon tanks in the post, but still very ignorant puttings of fish indeed.
Solitary brown bullhead catfish I caught in the lake by my house. I kept trying to give him friends. I tried crayfish and other fish from the lake but he obliterated everything I put in that tank that night. I'd just hear splashing and that was it. I even tried cichlids and a belonosox but no joy.... Now it all makes sense but I was 8 so it upset me so I put him back in the lake.