Just a tidbit of information

[easyian]

If anyone is running a Red Sea Prizm Pro and the pump is rattling it may be one of a couple of things. 1) The pump may be worn out. To check turn the impeller by hand you should feel resistance and it should not turn a full 360 degrees by itself. 2) The impeller has two white collars on top and below the magnet. If either of those has a space between magnet and the collar the impeller is bad. 3) The little bushings at the end of the impeller axle may be pressed on to far and not seating in the housing properly. This allows the impeller to move causing a rattle. The fist two come straight from the guys at Red Sea(who are not very prompt at returning e-mails) and the last thing I found on my own.

Just something to help. I have been fighting with this thing for a month and finally found the problem. The rattle from this thing was enough to put a person in the nut house.