I guess the best question is: what conditions do you have that you want a fish for?
I keep my BIG gold fish in the basement in an unheated tank. No aeration is needed because it's cold down there. Super easy!
I have very small fish like bettas and tini goldfish on the walls on the main level of my house.
Most fish you see in shops are fresh water as opposed to salties/brackish.
Or are you talking fresh water like fish you find in lakes and rivers?
Those are very hard to take care of. You need COLD tank system with very good air exchange and flow for those.
Last edited by a moderator: