Hi Caryl - Hang on to that one thanks!!!!!
I went into Jansens to return one that they had sold that was wrong. Originally they said they had no other models, but one of the helpful staff said he had seen one lying around that fitted the description.
Sure enough after a few minutes he came out with one for a 304 that looks identical to the one needed.
When I get home I'll try it in the 404 and see if it is the same part, if not I will buy your one thanks.
Also decided to bump up filtration and add a Aqua One 2400. The Fluval 404 will become the backup unit used on another tank. The CF2400 are a damn good price at $260, has any one been bitten by them or are they ok?