# Canister filter: What determines what size tank they can work on?



## crudnugget (Feb 5, 2008)

I am currently shopping for a canister filter for my 55 gallon lightly planted low tech tank. This question is not about brands, per se, but I will give two examples of what I am talking about.

First, the Eheim 2215. It is rated at 164 gallons per hour, yet is recommended for tanks up to 95 gallons. Then, the Rena Filstar XP1 is rated at 250 gallons per hour, but is only recommended for tanks up to 45 gallons. These recommended sizes are according to the pages on bigalsonline, but I have also been looking at this chart, which gives the same numbers for the XP1, but recommends the 2215 for 75 gallons.

I know with HOB filters, you can pretty much just go with the gallons per hour flow rate as a pretty good guide on what size tank they will do well on. Apparently this is not the case with canisters. Is the difference in how they are designed?

These are not the only two filters this question applies to, and I don't want to stir up any arguments about what brand is better


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## YankyTexan (Mar 8, 2008)

I can only speculate but I suspect some manufacturers report gph with media while others publish gph without media.

I had a FW 55g in wall setup for 9 years. I like redundancy (sp?) so I ran two small canister filters on the tank. Alternating cleanings and improving flow within the tank and if one failed the other would still be there.

IMHO you can never have too much filtration.

Good luck.


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## ColeMan (Mar 9, 2008)

A variety of factors help determine what size canister filter needs to be used on a particular sized tank, including bio-load, tank dimensions (is the tank long or wide) and in-line accessories among others. From what I recall, most filters are rated without media, so the manufacturer's suggested flow rate is usually max-flow with no media (the case with eheims, at least...). So, the manufacturers suggestions are just that, suggestions. INdividuals need to determine the proper amount of filtration based on their own particular needs; there's no magic formula here, just common sense. A few brief thoughts on some of these "factors."

Bio-load. Depending on the number of fish and/or plant density/mass, a larger or smaller filter may be required. More fish demand more filtration (obviously), and a more densely planted tank means more disruption/impediment to flow. Increased flow is especially important in this instance, as plant mass can reduce flow to a point that stagnant "dead spots" are created (little to no water movement, detritus build up, etc).

tank dimensions. a tank that is very long and narrow may need increased filtration despite the volume (gallons) indicating a "smaller" filter needs to be used. In this case, an extra inlet/efflux on the opposite side of the tank would greatly enhance circulation/flow, as water is being filtered (and returned) at both ends of the aquarium. A cubic tank that is the same volume may need only one filter, as a strong flow would not be as necessary because the return (filtered) water need not travel as far to reach the other "ends" of the tank... 

in-line accessories. Reactors, heaters and the like all impede flow to a certain degree, so depending on what kind of accessories you'll be using in-line, an extra filter may be necessary to compensate for the reduced flow. 

Biological filtration is not the issue here, but rather flow...The manufacturer's suggested tank size is adequate, no doubt, for simple questions regarding the minimum amount of biological filtration needed for a particular size tank with an average bioload. If you're deviating from this standard in any way (with increased bioload, plant mass, inline accessories, etc), then these guidelines become more or less useless. 

A good rule of thumb for a densely planted tank (this is debatable) is to aim for a turnover of 5x the tank volume per hour; so, your 55 would need ~250 gph of unimpeded flow...but of course, this is contingent upon many factors.


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## TheCryptKeeper (Mar 9, 2008)

I would personally go with a rena xp3.. but that is just my personal preference so... eheim guys don't flame me! I have a co2 reactor inline on one of my filters and it cuts down the flow a little.. and a uv sterilizer on the other side and it doesn't do much restricting at all. but it does a little bit


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## lescarpentier (Feb 2, 2008)

ColeMan said:


> From what I recall, most filters are rated without media, so the manufacturer's suggested flow rate is usually max-flow with no media (the case with eheims, at least...).


What Eheims? Pro II,Liberty's,Ecco's? It has already been determined that the Classics provide the same flow with or without media.



ColeMan said:


> tank dimensions. a tank that is very long and narrow may need increased filtration despite the volume (gallons) indicating a "smaller" filter needs to be used.


So you are saying that if increased filtration is needed,it indicates the need for a smaller filter?I don't know how you came up with that but I cannot disagree enough with that statement.Try using the search feature.There is a lot of valuable information on this site regarding this.


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## crudnugget (Feb 5, 2008)

What I believe ColeMan was trying to say, is that longer tanks should have more gph than a shorter tank of the same gallons. For instance, a 55 gallon that is 48" long would need a "bigger" filter, while a 55 gallon that is 24" (which probably doesn't exist, just an example) could do with a "smaller" filter.

My tank is very lightly planted and has a small bio-load. I do not plan on having any inline equipment. 

Heavily considering the Eheim Classic 2217, on sale for ~$115 at bigal's.

edit: I did use the search feature, and got a lot of threads about who liked what filters. I was mostly asking why GPH didn't seem to correlate to tank size recommendations between manufacturers.


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## fshfanatic (Apr 20, 2006)

Its more the volume of media which the individual filters hold that determines the size of a tank in which it will support than it is the amount of water it will push.


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## Gad (Apr 6, 2008)

fshfanatic said:


> Its more the volume of media which the individual filters hold that determines the size of a tank in which it will support than it is the amount of water it will push.


Correct answer. And type.


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## macclellan (Dec 22, 2006)

fshfanatic said:


> Its more the volume of media which the individual filters hold that determines the size of a tank in which it will support than it is the amount of water it will push.


Flow and filtration are two separate things. Both are important. A filter typically provides both flow and filtration. For example, an XP3 is sufficient filtration for a 90g. However, it is inadequate flow. Adding powerheads etc. compensates for this, but puts more junk in the tank. Using a larger filter, with respect to filtration, is unnecessary, but a larger filter typically means increased flow rates as well. I prefer to put all my junk in the trunk, so I'd opt for a XP4 on a 90g.

More directly to the OP, an XP2 is sufficient, but given the minimal difference in cost and energy consumption, and the significant increase in flowrate, an XP3 is better.


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## fshfanatic (Apr 20, 2006)

macclellan said:


> Flow and filtration are two separate things. Both are important. A filter typically provides both flow and filtration. For example, an XP3 is sufficient filtration for a 90g. However, it is inadequate flow. Adding powerheads etc. compensates for this, but puts more junk in the tank. Using a larger filter, with respect to filtration, is unnecessary, but a larger filter typically means increased flow rates as well. I prefer to put all my junk in the trunk, so I'd opt for a XP4 on a 90g.
> 
> More directly to the OP, an XP2 is sufficient, but given the minimal difference in cost and energy consumption, and the significant increase in flowrate, an XP3 is better.


I understand that. I was addressing the OP's original post in regards to what determines what size tank they can work on. I make my decision based on media volume not flow rate. Plus, generally the larger the media capacity is the higher the flow rate of a canister will be.


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## macclellan (Dec 22, 2006)

Yes, but my point was that adequate media volume is generally reached before flow rate is, going up a company's filter line. So, basing one's choice simply by meeting a criterion of adequate media volume will result in an inadequate filter choice, all things considered. An XP2 "can work" on a 55g in the sense that the biomedia volume will be sufficient. Still, flow would probably be insufficient in a heavily planted tank, meaning that media volume alone isn't adequate to make the correct decision. I make my decision on media volume and flow rate.

FYI: I have an XP1 on a 30g and would say that the flow rate is adequate. I would use a filter with a higher flow rate on a 55. At least an XP2 if not XP3, if you went Rena (of which I have three). I only have one Eheim, so I won't comment on them.


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## fshfanatic (Apr 20, 2006)

Good point.

Looking at it that way, I do as well. I am a firm believer in "Over Filtration".

I think we agree with each other. Just having issues saying what I am thinking this am.. I need a beer.


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## macclellan (Dec 22, 2006)

Yes, cheers to beers and overfiltration!


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## Gad (Apr 6, 2008)

Somebody say beer?


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## fshfanatic (Apr 20, 2006)

Yup! I always keep a couple 18pks of 16ozers in the icebox. Sporting that sig pick you are always welcome to swing by for a cold one and a cigar!


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## Gad (Apr 6, 2008)

fshfanatic said:


> Yup! I always keep a couple 18pks of 16ozers in the icebox. Sporting that sig pick you are always welcome to swing by for a cold one and a cigar!


Thanks, but the beer I drink doesn't come in 18 packs or 16 ouncers. Bottles and pints only. And it can't have rice in it.


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## fshfanatic (Apr 20, 2006)

I also have some







and Sierra Nevada Pale Ale, a fifth of Jamison, Grey Goose, Kettle One and Patron.


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## Gad (Apr 6, 2008)

fshfanatic said:


> I also have some
> 
> 
> 
> ...


I'm on my way.roud:


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## fshfanatic (Apr 20, 2006)

I will leave the light on!:thumbsup:


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## crudnugget (Feb 5, 2008)

Glad this thread turned into something civilized


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## ColeMan (Mar 9, 2008)

lescarpentier said:


> What Eheims? Pro II,Liberty's,Ecco's? It has already been determined that the Classics provide the same flow with or without media.
> 
> 
> 
> So you are saying that if increased filtration is needed,it indicates the need for a smaller filter?I don't know how you came up with that but I cannot disagree enough with that statement.Try using the search feature.There is a lot of valuable information on this site regarding this.


Perhaps I wasn't clear enough in my first post; crudnugget seemed to get it (at least in part), but you obviously missed my point. 
Let me make this more clear: A long, narrow tank most likely needs increased FLOW (this is what I should have said) even though the manufacturer's "tank rating" says it will work for a 75 gallon. "A tank that is long and narrow may need increased filtration (a larger filter) despite the fact that a manufacturer may recommend _____ filter ( a smaller filter) for a 50 gallon; the tank's shape, at least to some extent, dictates how much filtration (i.e. flow) is needed...does this make sense? 

AS for the first quote about the flow rate with media, I meant after the media has had time to get dirty...if you're trying to tell me that a 6 month old filter will have the same flow as a clean, new filter, I don't believe you. This wasn't clear in my first post, so I hope this sets things straight. 

And, by the way, I don't appreciate the comment about the search feature. I know how to do a search. You don't have to insult me. I got your point without the flame, thanks. Why is everyone been so quick to jump down everyone's throat, lately?


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## ColeMan (Mar 9, 2008)

lescarpentier said:


> What Eheims? Pro II,Liberty's,Ecco's? It has already been determined that the Classics provide the same flow with or without media.


I might also mention that YOU determined this (for which we are all appreciative). AS mentioned in the post on the top of page 3 here http://www.plantedtank.net/forums/equipment/63687-eheim-2215-2217-facts-diy-performance-3.html#post581364

"The maximum flow rate of the unit is determined without filter media at zero head pressure. You might loose 10-15% of flow once the filter is full of filter media at a distance of 4ft. 

Please do not hesitate to contact me if you require further assistance. 

Yours truly,

Ernesto Cedeno

Technical Support"

That said, I wholeheartedly stand by my original post. Hope I clarified things a bit above.


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## TheCryptKeeper (Mar 9, 2008)

macclellan said:


> Yes, cheers to beers and overfiltration!


kudos! overfiltration is where it is at! I have 2 xp3's on a 75 gallon!


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## macclellan (Dec 22, 2006)

On my 75g, I've got an XP3 and Eheim's 2227, the wet-dry biological monster-canister filter. But it is an insanely overstocked Mbuna tank.


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## lescarpentier (Feb 2, 2008)

ColeMan said:


> I might also mention that YOU determined this (for which we are all appreciative)


I see your veiled implication,but that is OK. You do not have to believe my figures,and I encourage you to attempt to disprove them,and to try to discredit my work.You are also free to believe everything that Ernesto claims.



ColeMan said:


> AS mentioned in the post on the top of page 3 here "The maximum flow rate of the unit is determined without filter media at zero head pressure. You might loose 10-15% of flow once the filter is full of filter media at a distance of 4ft.


Again,a determined search of the forum would reveal to you the information provided on the Pro II boxes.The information on these boxes indicate an approximate loss of 29% of flow with media.Ernesto claims 10-15%.Which information is correct? It is any body's guess.In addition,Ernesto does not specify a specific model of filter.Classic,Ecco,Liberty,Pro II?I doubt that I am the only person seeing red flags here.This information that he provided means absolutely nothing to me,except to confirm my doubts.



ColeMan said:


> That said, I wholeheartedly stand by my original post. Hope I clarified things a bit above.


This is fine too.I reread your post,and came to the same conclusion.
I also stand by mine.


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## ColeMan (Mar 9, 2008)

I'm in no way trying to discredit anything you've done (and I was beinf serious when I said we're all appreciative)...I believe your figures...but in my original post I was simply talking about "most filters" - not any one in particular. I think you and I are on the same page as regards to flow loss--it happens, that's all I was trying to suggest; the degree to which it happens, well, I'll leave that up to someone like you to figure out!! 

Do you see the point I was making in my original post about tank dimensions dictating, at least in some way, how much filtration is required (to get adequate flow)? And do you understand that I was not trying to suggest that a tank that needed more filtration needed a smaller filter? I am in no way trying to be contrary or dismissive of your results - like I said I was talking about filters in general, I just happened to mention eheim. I still don't get why you think I need to do a search to find out about flow rates for the Pro II? I don't understand what point you're trying to make? I just don't understand what we;re disagreeing about?

I think that we're in agreement on most issues, but I don't think I worded the first post in the best possible manner...I hate it when I can't figure out what's going on!!


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## fshfanatic (Apr 20, 2006)

macclellan said:


> On my 75g, I've got an XP3 and Eheim's 2227, the wet-dry biological monster-canister filter. But it is an insanely overstocked Mbuna tank.


Thats it? On my 125 I have an FX5 and a Pro II 2026 - My 180 has a Classic 2260 and 2217. :thumbsup:


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## lescarpentier (Feb 2, 2008)

I do see your point about tank dimensions,however I think that "smaller" should be edited to say "larger".Then I would agree with it wholeheartedly.

You posted Ernesto's reply to make a point,and I responded to it.I am reluctant to believe that you would have used his figures had you known about the information on the Pro II boxes,hence the search comment.

I think that we all have the responsibility to provide information that we are certain about,and we must word our posts in such a way to avoid the possibility of ambiguity for which forum posts are noted.

Peace!


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## ColeMan (Mar 9, 2008)

I completely agree...When I posted originally, I was in the middle of doing yard work, so I was rushed. Smaller should in fact say larger...an oversight on my part. I get what you're saying about the Pro II series now, and you're most likely correct. I was the associate editor of a newspaper for many years, and am right on track with you as far as minimizing ambiguity to reduce confusion, especially in this case since the OP was asking a fairly fundamental question, whose understanding (or lack there of) could lead to a misunderstanding about aquarium basics, in this case, canister filters. 

I edit my posts whenever I notice a mistake (even punctuation, i'm crazy), and I'll be sure to edit this one as mentioned...after I read it again after not looking at it for a while, I noticed the not only the ambiguity, but also where the confusion originated from. I might add I've been taking pain medicine lately, which, although no excuse, can't be conducive to intelligent, lucid writing! It means a lot to me that you took the time to set things straight; i was getting so frustrated because i value your opinion (especially after that eheim thread - you know the one) and so thought we;d be on the same page. As a matter of fact, when I was first typing my response I almost wrote something like - "Looking forward to hearing les' response" or something to this effect, because, as mentioned, I trust and respect your thoughts and opinions. Hopefully the same can be said about me (at least someday), as I always try to provide the best info I have and will absolutely not post a response if I don't have a legitimate answer (or source, at least).


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## TheCryptKeeper (Mar 9, 2008)

fshfanatic said:


> Thats it? On my 125 I have an FX5 and a Pro II 2026 - My 180 has a Classic 2260 and 2217. :thumbsup:



ok... its on now! lol!


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## PDX-PLT (Feb 14, 2007)

There's a difference between mechanical and biological filtration as well. For mechanical filtration, the higher the flow, the better. For biological filtration, that's not necessarily the case - the velocity of the water through the the bio media needs to be low enough so that the bacteria can do their thing.

Different vendors have different criterion by which they design their systems; I've read the Eheim's are typically "low flow" to maximize biological filtration; some of the others are "high flow" to both maximize mechanical filtration, and to have impressive-sounding numbers.


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