The standard first tank here is a small bowl, two goldfish, and a fortnight of everybody being sad.
Goldfish are a bad beginner fish for reasons that have nothing to do with the fish being delicate. They get large, they produce a great deal of waste, they want cool water rather than a warm room, and a bowl gives them neither filtration nor surface area.
What actually works for a first tank:
- A bigger tank than feels necessary, because a larger volume is far more forgiving of mistakes
- A filter, cycled before any fish go in
- Fish that suit a warm room -- guppies, platies, mollies, tetras, danios
- Fewer fish than you want
- Feeding much less than feels right
The hardest part to explain to a child is cycling the tank, which means waiting weeks with no fish in it while the bacteria establish.
What was your first tank, what died, and what would you tell someone setting one up for a ten-year-old this weekend?