# Filter Sizing Confusion



## dlwhitt (Jun 26, 2010)

The research for sizing a filter for my new 90 gallon tank is confusing. Filters have an aquarium size rating and gallons per hour flow rate specifications. Those two measuring tools rarely correlate when factoring the most semmingly appropriate sizing measure of tank water capacity turnover rate. It appears that 3 to 5 times per hour are the most recommended turnover rates. Is there a best turnover rate rule that I should use to size a filter?


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## rgr4475 (Mar 19, 2008)

Keep in mind that most of the posted GPH are with an empty filter with no media. Also do not go by the aquarium rating size at all. I go buy Gallons Per Hour. Knowing that I like to go 10x per hour turn over rate. You will probably be fine with less assuming your tank isn't overstocked. I just prefer to over filter some.


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## kmuda (Nov 27, 2009)

I place zero faith in filter manufacturer recommendations. For instance, while an Eheim 2217 is an absolutely great filter, perhaps the best ever made, Eheim states it's good for a 160 gallon tank and I would not be comfortable with it (solo) on anything larger than a 55. But I generally deal with large South American Cichlids, were massive filtration is a must.

Do you have any filters in mind? If you mention what specific models you are interested in I can provide recommendations on if I would consider it acceptable or not.

On a 90 gallon, as a solo filter, either a Marineland C-360 or a Rena XP3 would do the job, although if it were my tank I would run them in conjunction with an HOB.


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## dlwhitt (Jun 26, 2010)

Hello kmuda,

The filter that I have in mind is an Eheim Professional 3 2075 that has a rating of 290 gallons per hour that provides just over a 3X per hour turnover rate. I would ideally like to use the 2080 model rated at 450 gallons per hour suplying a 5X turnover rate, but the vertical clearance is too tight in the corner positioned built-in cabinet supporting the tank. An HOB isn't practical because of the minimum rear clearance between the tank and wall. I'll most likely populate the tank with a Malawi mix with eventual stocking on the heavy side.

My confusion is about what's really needed for optimal water filtering with a resulting best environment. Surely there's a point of diminshing returns, and overkill filtering for the sake of some perceived only benefit - but what is that level? 3X, 5X or as much as a 10X turnover rate?? Even dual 2075's only provide a 6X turnover rate...

Thanks in advance for you and other's time and guidance.


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## aquariam (Feb 11, 2010)

I suggest you get TWO Eheim 2217's for a similar price. Higher overall volume, and 500GPH-ish

Don't discount the 'classic range'. They are excellent. They aren't as fancy, the media is a bit more of a PITA to service, but you get excellent affordable filtration.


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## gmaschke (Aug 23, 2008)

I trust manufacturer ratings..... after I divide them by 2!


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## aquariam (Feb 11, 2010)

gmaschke said:


> I trust manufacturer ratings..... after I divide them by 2!


I always gave them an extra inch and assumed about 65% myself  

I've heard that Eheim advertises the flow freshly set up with the recommended media though, not empty. Don't know if it's true.


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## kmuda (Nov 27, 2009)

The 2075 is a very efficient filter. Biologically, it will certainly suffice. I would be concerned with sufficient mechanical filtration with a turn over of 3x per hour.

I do like the idea of a pair of 2217's. Two filters is always better than one and this would bump your turnover up to a "best practice" range. Would not cost substantially more than a solo 2975.

I use the Eheim Classics extensively (currently have four of them) and can testify they are great filters.


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## dlwhitt (Jun 26, 2010)

How can I get sufficient mechanical filtering without an HOB? What is the "best practice" turnover rate range - point of diminshing returns and overkill filtering?? 3X, 5X or as much as a 10X turnover rate???


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## BillD (May 17, 2005)

Keep in mind that there is hardly a poster on here that doesn't know much more than the manufacturer about filter capacity. It is a wonder these companies stay in business.
There are always a few things that disturb me in these discussions. Things like concern for mechanical filtration with a 3 time turnover. How is it beneficial to have all the sold crud trapped in a filter instead of visible so it can be removed with a ater change. It never ceases to amuse me when the same people who insist you need big filtration don't clean their filters for 6 months or longer. This is akin to not cleaning the tank for that period, as everything in the filter needs to be considered still in the tank.
It is a shame that the filter manufacturers have hired incompetants to design their filters, when there are thousands who know so much more about filtration, and so freely offer their advice.


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## fox (Jun 11, 2009)

dlwhitt said:


> How can I get sufficient mechanical filtering without an HOB? What is the "best practice" turnover rate range - point of diminshing returns and overkill filtering?? 3X, 5X or as much as a 10X turnover rate???


Hydro-Sponge filter. Get the coarse sponge for longer maintenance life.

3X's is recommended for proper bio filtration. I use two different types of filtration on all my tanks and aim for higher than 7X's combined.

I strive for the "Fish floating in air" look.


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## aquariam (Feb 11, 2010)

You can't overfilter. You can overcurrent. For some species you can over oxygenate. The latter is difficult to do.

Overcurrent can be prevented while "overfiltering" by diffusing the output of a filter. for example, on the 2217, connect two spraybars together, then put a sponge on the end. The resulting 250ish GPH output will barely more any water at all. You can put two of them on your tank in this method and barely see any water movement for their 500GPH.

You have many different options here. They include but are not limited to-

2x 2217

1x your original choice, which is a good filter, + 1 large hydrosponge run by a powerhead ideally, but airpump works too.

1x your original choice + an Aquaclear 110 for mechanical filtration

etc


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## kmuda (Nov 27, 2009)

BillD said:


> Things like concern for mechanical filtration with a 3 time turnover. How is it beneficial to have all the sold crud trapped in a filter instead of visible so it can be removed with a ater change.


You will never gravel vac out of a tank what can be removed via mechanical filtration in that gravel vacs are not as efficient. Regardless of how diligent you are, you will not cover every inch of the substrate and quite a bit gets left behind. Effective mechanical filtration in conjunction with gravel vacs is the recommendation.

Two things effect mechanical filtration, surface area (as in width and depth) and flow rate. The higher the flow and the larger the mechanical filter media surface, the more effective it is. But you are right, if you are not diligent in your maintenance practices mechanical filtration serves no functional purpose. Your better off letting the gunk collect in the substrate and removing it via gravel vacs.... and for this to be effective, you need to have a low turnover.



BillD said:


> It never ceases to amuse me when the same people who insist you need big filtration don't clean their filters for 6 months or longer.


My standing recommendation is an HOB (optimized for mechanical) with a canister (optimized for bacterial), with the mechanical media cleaned weekly and the canisters cleaned monthly. If you wait until it _needs_ cleaned, you waited too long.



BillD said:


> It is a shame that the filter manufacturers have hired incompetants to design their filters, when there are thousands who know so much more about filtration, and so freely offer their advice.


If it were the people designing the filters who were the sole individuals responsible for proposing the recommended tank sizes the numbers would likely be different and would be more trustworthy. However, corporations have large marketing departments with input designed more to sale product than to help us out. In too many instances, it is the recommendations from the marketing folks that wind up on the box cover.


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## aquariam (Feb 11, 2010)

kmuda said:


> BillD said:
> 
> 
> > Things like concern for mechanical filtration with a 3 time turnover. How is it beneficial to have all the sold crud trapped in a filter instead of visible so it can be removed with a ater change.
> ...





kmuda said:


> I place zero faith in filter manufacturer recommendations. For instance, while an Eheim 2217 is an absolutely great filter, perhaps the best ever made, Eheim states it's good for a 160 gallon tank and I would not be comfortable with it (solo) on anything larger than a 55. But I generally deal with large South American Cichlids, were massive filtration is a must.


 I 100% agree with everything kmuda has said in this thread. :thumb:


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## dlwhitt (Jun 26, 2010)

My conclusion is that there's not an established "best practice" water filtering turnover rate that produces the optimal water quality without exceeding the unknown point of diminshing returns and subsequent overfiltering. I now believe that there are too many tank variables to have a single recommendation, and that the best approach is to separately address the biological and mechanical filtration requirements. That method allows both processes to contribute to the overall combined water filtering turnover rate, with a probable best total of more than 5X and less than 10X per hour.

I intend to initially use an Eheim Professional 3 2075 providing a "manufacturer rating" of 3X per hour turnover rate for biological filtration - the Professional series won over the Classic series because of the convenience functions and features. I also intend to use a Hydro-Sponge filter having a coarse sponge run by a powerhead providing a yet to be determined hourly turnover rate for the mechanical filtration. I'll add another 2075 for supplementary biological filteration and equipment redundancy as the Malawi mix juveniles mature to an eventual tank stocking on the heavy side.

I'll post my future results so as to hopefully help those having my similar filter sizing confusion. Thanks so much to all of you who contributed to this subject. The time taken for your valuable guidance was genuiniely appreciated. This site has given me an incredible education as I return to cichlid fish keeping after a way too long interval of being without that pleasure. I look forward to eventually being able to contribute some of my knowledge aquired through experience, but my posts for some time will necessarily be of the asking versus telling variety!


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## noddy (Nov 20, 2006)

I think you have "done the right thing", in that you have took on board all the advise and drawn your own conclusions. For what it's worth, I have three heavily stocked Tropheus tanks, one is filtered by two 2217's and a maxi-jet 1200 hooked up to two #5 sponges. One is filtered by one 2217 and the same sponge/powerhead set-up and the third one is filtered by two sets of double sponge/powerhead only. I use purigen in each of my eheims also. The 2075's look like a very good filter.


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## Ali1 (Apr 7, 2005)

Clarify this for me.

Why is the turnover rate so important? IMO, as long as you have enough bio filtration for the breakdown of ammonia/nitrite in your tank, you should be fine. I do large water changes every Saturday.


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## kmuda (Nov 27, 2009)

Ali1 said:



> Clarify this for me.
> 
> Why is the turnover rate so important?


Numerous reasons.

1. The higher the turnover, the more air exchange that will occur, which impacts O2 levels, which impacts not only fish health but beneficial bacteria efficiency.

2. Nitrifying bacteria do not actively seek out ammonia and nitrite. It has to be brought to them. If the turnover rate is too low, ammonia levels can build up in the tank faster than the bacteria can remove it. Think of the check out lines at Wal-Mart. If only one or two cashiers are working, people start to back up in line. Add more cashiers and people spend less time in line, unless you have a ton more people (overstocking) than the cashiers can possibly keep up with. In this scenario, the cashiers are the "flow rate" and the people standing in line are the ammonia and nitrite. The object, in our tanks, is to have very little "wait time".

3. Mechanical filtration is significantly impacted by flow rates. The higher the flow, the more gunk that will be brought into the filter (where it can be easily removed) instead of settling into the substrate.


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## hcubed (Sep 3, 2010)

I know this thread is a little dated, but the topic is still just as relevant today as when it was started.

I am also experiencing confusion and frustration over filter sizing. I had a Fluval 403 I was happy with for a long time on my 55. I knew a lot less then, but it still worked with a huge Oscar. It recently became too loud for me to tolerate, so after a new impeller didn't fix it, I bought a new Fluval 405.

I read a lot about Fluvals and Eheims. I didn't find an Eheim that seemed sized for my 55 gallon, especially considering the overfilter motto. I found the Eheim 2260 rated for 396 gph. That seems like over-filtering to me, but it's also $100+ more than the Fluval 405--if I can even find a 2260. The Fluval 403 was rated at 317 gph and got by all these years. The Fluval is rated 340 gph new for $149. I bought the 405. Now it's not quite as quiet as I'd hoped, and it seems more cheaply built than the 403.

I just learned about the Eheim 2217 rated 264 gph and read recommendations here for it used on a 55 gallon. However, it's not 8 times turnover per hour. Add to this the fact that these gph ratings are pump output. In the Fluval 405 manual, it states in one real-life setup the actual water turnover is 225 gph. Add to this the fact that everyone packs different media differently and has a little different hose, intake, output arrangement, how is anyone supposed to make an informed decision?

Sure, overfilter, but I live on a budget. I can't buy (nor do I like the thought of paying for) a $400 for a filter if I thought a $200 filter would do a more-than-adequate job.


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## BillD (May 17, 2005)

I'm with you hcubed. Any filter that gets ammonia and nitrate down to 0ppm, is a good filter. Adding filtration, beyond this adds redundancy in the event of a failure (assuming 2 units, not one very large filter), but doesn't improve the filtration. IF you have 2 filters, each of adequate size for the bioload, each will do half the job. None of this takes into account the effect of the nitrifying bacteria not in the filter. There are huge numbers of tanks running with nothing more than sponge filters, at a small fraction of the cost of a name brand cannister. Personally, before I spent even $200 for a filter, I would buy a new 75 gallon tank, lights, substrate and filters, and still be a few dollars ahead. This hobby can be enjoyable without spending huge amounts of cash on equipment, and not everyone can spend those dollars. For those people the hobby is still in reach, with alternative types of equipment.


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## PfunMo (Jul 30, 2009)

I appreciate that you plan to post your results but I'm afraid it will do little to lessen the discussion. This is almost as old as the chicken and the egg argument. Everybody knows but nobody believes-- unless it agrees with what he knows. With that in mind, I just go with a filter that feels right and then be prepared to adjust. I think you will find there are no tanks set up, stocked, and fed exactly like your tank. All of these plus how you want to maintain your tank make it pretty much a personal decision. Perhaps in a few years you can tell us what is the true answer??? :roll: :lol:

It does sound like your answer is based on what should work for you. Welcome back to the hobby. :thumb:


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