Hynobius are vso easy to take care for (if they arrive in good health) . The only thing you don't wanna do with them is clean their tank each week... I think this works aversely. I use lots of wed moss and forrest litter in the landphase (raising tanks for juveniles) and the breeding tanks only get changed with fresh water in the spring time (many times shortly after each e other). I know it might sound silly but I think one of the problems with these guys in the past may have to be 'over-caring'. Also try to keep them not too warm. I keep them in a gardenhouse. In fact they resemble Ambystoma in so many ways :humidity, tank installation , food. Breeding ofcourse is somewhat different but not that much : they also need twigs and branches (like A. gracile for instance). If you need more info tell me ... or wait a bit to see my H. dunni care sheet I will post on caudata.org in a while (shpoudl have been finished already ... but I'm running late as ever).