Not sure if you are still looking for a CruiseFish replacement, but I'm using a new app called Cruise Pop. It seems to be in it's early stages and by referral / invite only. I believe it only works with
Royal Caribbean and Carnival at the moment, but it's free and so far I've had great success with it. You can submit your alert requests using the Google form located below:
The forum thinks my link is spam, so I guess PM if you want the link.