I know, older thread, but just a quick note.
As for the reverse flow that some have experienced, me included, its easy to put back to correct. Simply power down the unit and power back up. It might take a few tries, but it will go back to correct operation. Also, make sure you keep them clean. 4 months max between cleanings. As mentioned, soak in vinegar for 1/2 an hour, wipe down and rinse. Make sure you pull the prop out during cleaning and make sure the magnet gets a good wipe down.
I have noticed that flow rapidly decreases the dirtier these get. My 2 750s were barely moving any water after 5 months. A quick cleaning and they were like new. couldn't believe they weren't pushing water until I cleaned them!