with the kind of aggression that these fish have i would say anything short of 300 gal and you have dead fish ..
there are many problems with the set up .. the fish he keeps the size of the tank and the knowledge of the person in general are all wrong
this is why people need to ask before they buy not buy then ask if its ok ... you dont go to the store and buy a English mastiff and not know what your getting ... same as you dont get a teacup rat dog and expect it to be 300 lbs .. you learn first buy second .. his stock is not really the most compatable the tank is WAY to small ... but then again .. its prolly just a troll posting stuff to get members all in a fussy .. who knows .. i guess pics would be proof ..
im not saying that you advice is not wanted .. its just not 100% correct .. but then again you pointed out that your a small planted tank kind of person ..