I saw a promotional Eheim video with an american voice over (they're german aren't they?) and he pronounced it "A-Hime" (Hime asin rhyming with "Time")
I felt like a right prat going into a fish shop a few weeks ago and wanted some cichlids, but was'nt sure how to pronounce it, just said i want a couple of those and the guy pronounced it lol. Can't stop saying it now lol.