I kept them for a couple of years and they were realy neat. We used to get the odd one when taking tubifex from the south branch of the Waimakariri river. We fed them mainly tubifex worms and they would stick to the side of the tank like sucking catfish. Mine were small, about the size of the old 50c piece. I had no refrigeration and suspect they died from getting too hot in summer. Great fish if you can get them. That was 30 years ago and the tubifex has pretty well gone so if that was the atraction they may not be there now. There is I suspect a minimum take size.