I haven't ever had a rena, but I hear good things about them. I have a fluval on my 46 and its OK but a pita to prime and get going once you've taken it apart. Luckily I don't take it apart except every once in a blue moon. On my 29 and my 55 I have Eheims and I LOVE them. Don't forget to check prices at bigals and foster and smith websites. I got all three of them from bigals (maybe two at bigals and one at F&S? but all online) and you can save a LOT of money. I know I was actually going for another fluval, when I realized that an eheim was actually not THAT much more, both including filter media...so do your pricing carefully.