I have a 403 that I HATE (for sale cheap if you want it) as it would leak and could not get it to prime very easy, replace with two 304's that prime like a cham and they don't leak and cause water everyware!!
PS Priming is just simply getting the water flowing, in the x03 series of fluval's it was recomended that you put them on there side of tiped them back and forth to get the water flowing at full blast.
Good luck, hey as Red Green would say I am sure that Duck Tape would fix that...
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