I currently keep two speices; Pseudomystus siamensis and Microglanis iheringi. I also know of Batrochoglanis raninus, Pseudopimelodus bufonis, Pseudomystus aff. leiacanthus and Microsynodontis batesii which species are you talking about? Microglanis iheringi are unlikely to eat smaller fish as they are small themselves but anything they can fit into their mouths will disappear.