I bought two Koralia #4's after they were released last year. I really loved them in all ways but after about six months, they both quit on me within a week of one another. I was sooo disappointed and needed to replace them but couldn't buy something that wasnl't going to last. I saw a posting by Jeremy somewhere and he said he'd contacted Hydor and they replaced a PH for him. Jeremy helped me find the link so I emailed them. It took several emails to "gently" get them to say they would replace my Koralia (I had two, but had "robbed" the magnet from one for a MJ mod and thrown the rest away.) When I sent the PH to them with copies of our emails back and forth, I wrote a note saying I was sending in my lone existing Koralia but that I'd had two and robbed the magnet from one. It was the truth and what did I have to lose? My mail just came, with a package from Hydor with TWO new #4's. WOOO HOOO, can you believe it?? I'm a very happy customer at this point and thrilled to get those Koralia's back in my tank. I really prefer them over the MJ mod and Tunze 6045 combination that I have in their now. Happy customer for sure!!