Never had a fish tank (though plenty of bowls for goldfish won at the fair.. Is that still a thing? I doubt it).
A friend had an aquarium tank and I recall it being a lot of work when it came to cleaning it. But as has been said here, he found keeping fish strangely addictive.
I did have a garden pond once. It was dry and full of weeds when I moved to the house so I cleaned it out, relined it, filled it with stream water (there was one running through the garden) and planted it up with oxygenating plants.
I have to say it was one of the most rewarding garden features I've ever had. I could while away many an hour just looking into it to see what had taken up residence.
The shine came off it somewhat when a hedgehog fell in one night and drowned. I discovered garden ponds should have a shallow pebble beach so that creatures that fall in can walk out again. Lesson learned. Never had fish in it as next door's cat would have never left them alone, but it was deeply satisfying to see wildlife move in to something I'd created.
I'd definitely have another garden pond when circumstances allow. My dream would be to have a wild swimming pond.
