Somewhat childish, poorly-worded questions...I thought you were better than that.
- It depends on the water conditions, the number of times you'd be prepared to change the water and whether or not you'd want the fish to thrive or survive.
- See above, but add that no fish 'needs' an aquarium, never mind a 'smallest' aquarium.
- An infinite variety...such is the power of nature and genes.
Not bothered in the slightest about 'Likes'.
A true 'obsession' would take a holistic approach to the subject. (Look it up).
...And with that, my entire world falls apart!