I run twin 2217's on my 65g. And it's 36X18X24H. Myself I never run 4 footers on less than 2 canisters.
Just my opinion, but I really like the advantage of alternating a thorough cleaning of 1 canister and not stressing about losing bacteria.
If budget was the issue, I would try and buy 2 sunsun filters before one 2217. I have sun sun and eheims through out my house on various tanks and they both get the job done.
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