I disagree, not for 4 or more.I dont think this is accurate, a 6 foot tank is all you need. 125 or 150 would do.
Now that I think about it they would need a 6ft tank that's at least 3 feet deep. 18" wouldn't be enough for a full grown to turn comfortablely in.I disagree, not for 4 or more.
You would need room for them to actually swim without crashing with one another.
They are skiddish and extremely fast!
My bala has killed several fish over her ramming them.