I rescued an aquarium from certain uselesness before the trash trucks could haul it away. (Yes, my hobby has me trash digging.)
With a little bit of knowledge I think I understand why it was given such an ignoble end. The tank itself had a 3" wide band of calcium build up around the top and the gravel was filthy. From that I can extrapulate that water changes were rarely done if ever at all. Looks to me like a top off was all the previous owner felt was necesary. I can only hope they had enough sense to use a conditioner but I doubt it.
The small canister filter was rated at 80gph and imo didn't provide the kind of turnover needed to provide proper filtration for a regularly stocked tank. When I cleaned it I got another clue as to what happened to this tank. The sleeve sponge looked and felt like a glob of industrial sludge yet when I cleaned it up it apeared brand new. The charcoal sock was so grotesque that I put it in a sealed baggie and threw it away. The bio material had globs of gunk here and thier and was fighting a loseing battle. This filter never once had been cleaned.
So here's what I think happened. They bought the tank and took recomendations from a kid making minimum wage who sold them everything they needed without much regard as to what was actually required.
"Yes this filter has everthing in it you need and you'll also need a thermometer, some gravel, a heater, (this ones cheap) and a couple of rocks and some plastic plants."
"Now lets get you some fish. Sure, they all get along. You might also want to get an algae eater. These plecos are really nice. Your really going to like this aquarium."
Now they get the fish home, put water in the tank hook up the equipment and fill it with water. A couple of days later a few of the fish die. No big woop we'll just go get a couple more, thier cheap. A couple more die and this time thier a little aggrevated when they go back to the store. "Yea it happens sometimes and I'm so sorry. I can give you half price for a couple of these. Oh yea, they'll get along."
For a while everything goes along just fine but then they start dying off again and the new aquariest loads up on meds but they just keep dying. This is when the frustration really sets in and off to the curb the aquarium goes. "I'll never keep fish again."
They say ignorance is bliss but I doubt our fish would think so. Pass on the good knowledge my friends and it will be a rewarding experience for everybody including our captive friends.