Questions - Need some input

A few months ago I got a Sea Hare to help with cleanup duties... After 2 weeks it died... My wife loved the little guy and looked for it every day... I have learned they can be difficult to keep, with a very high death rate... I have researched the web and can't find any good info on how to keep it living other than good water quality and that is still no guarantee of success... Any insight would be helpful... Thanks