Type locality, Sungai Belalong, in front and near to Kuala Belalong Field Studies Centre, UNB uncat. (holotype of Gastromyzon cranbrooki, 4.82 cm SL). Presently known only from the Temburong River basin in Brunei Darussalam (Ref. 56228). This is the most common species of the genus in the riffle zones of Sungai Belalong (Ref. 56228).