maybe 9 or 10 yo and running around the school yard with jars of guppies, selling them for a few cents or giving them away, with a blue container of DeChlor in my hand telling kids to buy some, since we had a million guppies, I was trying to find them homes, so sad they probably all died in a couple days.
Going on vacation and leaving my fish tank in the care of a teenager (who had fish since small child and should have known better), and coming home from a 2 day, 1200 mile drive at almost midnight, exhausted, to find my tank with yellow opaque foul smelling water that was a little thinner, but almost the consistency of maple syrup. Then spending about three hours cleaning it. Only lost a some of the fish.
Going on vacation and leaving my tank in the care of my best friend, who had had fish since childhood, and dreamed of being a marine biologist, and had two 55G tanks of her own AND was going through a bad divorce...coming home to about 2 tablespoons of flaked food floating around on the bottom of my 16 G tank with very white Supernaturals sand, and several dead fish and a bamboo shrimp.
Buying 20 berried ghost shrimp, and putting them into a "cycled" tank, but I changed the filter pad every 6 weeks, and overstocked tank. They must have all given birth at the same time and the babies died causing an ammonia spike and a bacterial bloom and the water sparkled like superfine glitter in a completely opaque tank and couldn't see the fish.
Where I changed the filter pad every few days and did Pwc
every day or two and added several kinds of water conditioners and bacteria supplements, and overfed. No one at any of the pet stores knew what was happening and every store said to try something else. Finally after two weeks, I came to a store, and a new employee guy said let me get this guy he will know. I explain it all and he is looking at me with saucer eyes as I finish explaining it all and, I say what can I do. And he says......Nothing!!! Don't do anything else.
More or less, you have done too much already. He told me, although not quite all correctly, to just stop changing the filter pad and water and just wait it out for 21 days. (no water testing was recommended)
I know a lot more now that I am here! And it is surprising, some fish actually survived those events!