What is a Queen loach?
In the US the fish I have seen sold as queen loaches were Botia dario and only reach 6". I wonder if the one they sell here as Royal loach is the same thing as what you see as Queen loach, Leptobotia elongata, it reaches at least 24". I have not seen them for sale recently except for a couple listings in the UK.
The lepidocephalrichthys manipuerensis gets to 22", the L. irrorata reaches 15", I have never seen those. The catfish loach, Triplophysa siluroides gets 15" and is very predatory, I have only seen them for sale once years ago.
here is a pic of the L. elongata, and of the T. siluroides.