How much will you enjoy the fish in a 10 gallon? How much will it actually act like as warmouth and be a warmouth in a 10? If you just don’t want it to die- rock n roll, make sure you get a bottle of declorinsror and a pitcher or else a hose to siphon with. You’ll want to change some the water as it gets cloudy.
It’s always tough to answer a “minimum standard of care” question you can keep a fish wherever you want as long as you can. I think that the people asking minimum standard of care questions typically aren’t confident in there ability to provide anything else- which I guess points towards
Not for very long?