Betta vs Fancy Goldfish
The same axes for both animals, taken from the same care guides, so this is a like-for-like comparison rather than two articles written months apart. Neither animal is the right answer on its own — the question is which one fits the space, the budget and the routine you actually have.
How to read this
Every row is filled from the same field of the same care guide for both animals, so nothing here is cherry-picked to favour one of them.
Minimum space is the figure from each species' housing guidance, converted to one unit. It is a floor, not a target.
What this does not tell you: your experience, your household, your climate, or which animal you will actually enjoy. Difficulty is our judgement, not a measurement. Read both full guides before deciding — and if the honest answer is neither, that is a good outcome too.