Flow Rates External Filter Canisters

MrT

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I recently installed a flow meter to one of my aquariums external filter canister and I’m getting less than half the flow rates manufacture claims. No surprise there as I understand the physics involved and know that the stated flow rates are in a perfect non restricted loop, etc., etc. So my question is, what would be a actual measured flow rate for a typical aquarium? As an example one manufacture states flow rate for a certain external filter canister is 383 US GPM and they claim that makes it good for a 100 US Gallon Aquarium. Would it be safe to say that the manufacturer has a built in fudge factor because I’m sure they know that our actual real world flow rates are much lower? Continuing with this thought, would it be logical to say using actual measured flow rate of say 190 US GPH would be okay for a 100 US Gallon tank?
 

Dakotablue

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190 GPH on a 100 gallon tank is much lower than the recommended flow rate. A lot of people shoot for 10x water turnover in an hour. Depending on stocking I would generally recommend a minimum of 4x actual turnover.

I wouldn't follow their recommendations for "aquariums up to xxxgallons" I have an eheim 2217 (rated 264gph) on a 29gallon and I wouldn't want any less than that.
 

Dakotablue

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And welcome to fishlore! There are a lot of great people on here to help you out with your questions.
 

Thunder_o_b

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Greetings and welcome to Fishlore

That is true. My understanding is they rate flow with the filters with no medium in it.

This is where the practice of 10x or greater the water column in filter flow comes from. Then you add the drop off in flow as the filter does its job.
 
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MrT

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10x? Wow that’s no where near what is typically rated by manufacturers.
So to be safe, that would suggest using two 500 GPH filters for a 100 Gallon Aquarium with the understanding that you will certainly get the 4x in actual GPH.
 

Dakotablue

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Two 500's should do it, with the added bonus of being able to control the current better. Also gives you redundancy in case one filter quits on you when you're not around.

Overfiltering is better than under! Just don't blast your fish with a crazy strong current.
 

TLeTourneau

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Yeah, 10x is what I aim for too. I have a FX6 and FX4 on my 150 which give me a gross flow of 1625 GPH for a turnover of 10.83. I have a Reef Octopus Various-6 (1720 GPH) in my saltwater tank (73 gallon display, 91 gallon total) running at 55% for 946 GPH giving a turnover of 10.4 through the sump but that also has two wave makers providing 70x turnovers per hour in the tank.
 
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