When I was 15 or 16 (way back in the dark ages) my dad built a pond in the backyard (I have a photo somewhere of my friend and I swimming in it before he added the goldfish).
Up until then we had some goldfish inside in a bowl. Once a week they would get poured into a jug while the stones and bowl got scrubbed out in hot soapy water then rinsed, filled up with very cold water direct from the well, then the fish were thrown back in for another week. Not only did they survive this regime but they went on to live long productive lives in the pond.
Once married, Grant and I decided a fish tank would be interesting so we went to the local garden centre (our only option) and were told all the wrong things, sold the wrong things, sold the wrong fish - you name it, we did it wrong.
Then came an advert in the local paper from people wanting others interested in starting a fish club. We went to that meeting (Feb 1989) and have been in the Marlborough Aquarium Club, followed by the FNZAS (1992), ever since. Thankfully our fish keeping also improved once we were better informed (no internet or Google in those days!) and have acquired, over the years, an extensive fish keeping library.
At the height of our fish keeping we had 18 tanks spread throughout the house, including 2 or 3 each in the kids' rooms. This was because we often kept incompatible fish so always needed "just one more tank" to house the latest acquisition. We have kept tropical freshwater and cold and a local cold marine over the years.
We now only have 1 x 280L freshwater tropical, filled with geriatrics plus a few younger ones who keep spawning and so keep the fish levels relatively stable plus a large goldfish pond.