Make a temporary cave out of something that will drain as you pull it out or you can instantly close. I've pulled crazy loaches out of a planted tank by using a deep but narrow container that I could place a lid infront of and immediately block them in. Hopefully he's willing to try out the new cave. Otherwise, a pair of gloves, some buckets, and a tank dismantle is the only other way I know of that doesn't include a hook. GL