I'm comparing canister filters (for fun and future dream tank planning), and trying to understand how to apply the 10x filtration rule to them, and getting a bit confused.

For example with the Eheim 2028 it says:

Aquarium Size: Up to 158 U.S. Gallons
Pump Output: 277 U.S. Gallons/Hour
Filter Circulation: 198 U.S. Gallons/Hour

This may be a stupid question, but if it's pumping 277 gallons of water per hour, how is it only filtering 198 of those? Does some of it bypass the filter? Which of those numbers is the one that you use to decide how big of a tank you can use? I am assuming that the 158 gallon tank size they list is if you are keeping some sort of fish that doesn't make near the amount of mess that goldfish do, so that number gets thrown out right away, right?

Well what it means is that if you had the pump of the filter (so just the pump, no filter media or anything) it would pump at 277gallons/hr. However once you fill your filter with all its media, the flow rate goes down because it has to go through all the media, hence down to 198gallons/hr.

Your lucky it actually says that Most just put how much it pumps out, which isn't very accurate once the media is in it. You should go by the filter circulation part, more accurate

Okay well that makes sense, hadn't thought about the media slowing it down...

Yea filter media significantly slows down the flow rate. Alot of people really stuff their filters full of media, which is good and bad More filter media = more surface area for good bacteria to colonise, making for better filtration, however the filtration rate significantly slows down. Up to you what you want to do. I moderately stock my canisters, not really heavy.

I need another filter.. my banished cannibal has stolen one of the main filters!