Had a Koralia 4 running in my tank for about a year and it failed on me the other day. I notified the manufacturer and with no hesitation they asked me to send it in and they would send me out a new one. Talk about standing behind your product!
I am not sure of the name but the guy said there were a lot of units that were sold on e-bay that they are trying to get back Here is the address to send it to.
HYDOR USA Inc.
4147 North Bate blvd suite 6
Sacramento, ca 95834