On the new big Eheim you bought? What's wrong there? I honestly can't tell you about the manual cause I had them for so many yrs I don't even read that any more.
Now fluval I had one time; bought it hooked up, let run for few days ditched it I'm not even gonna repeat my feelings here towards that thing. They may have changed over the past 5yrs but I sure disliked mine and won't buy another one.
You know what thou when I looked for a good sized internal filter I came across these Cascades and I'm LOVING mine in the 45g.
LOL if you need a extra filter or 2 or 3
Just lemme know cause I promised hubby I'd get rid of all these spare tank parts here lol