# Can you have too big of a filter?



## aritg3 (Feb 18, 2008)

Just wongering, can you have too big of a filter on your tank? For instance, if you had 75 gal tank but a filter ment for 150gal tank.
-Ari


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## gtsum (Feb 25, 2008)

well, I do think you can have too much (i.e. a rena xp3 in a 20 gallon tank, etc), but having a 75 gallon tank and have filtration rated for a 150 is not overkill - it is likely the opposite (not enough). Cichlids need a LOT of filtration...I shoot for about 10x turnover (75 gallons = 750 gallons per hour). Of course other things will affect the water as well, but more filtration makes things a lot easier imo (not to mention lengthens the maintenance schedules, etc)


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## Toby_H (Apr 15, 2005)

The most common "rule of thumb" filtration recommendation for Cichlids is to filter the tanks volume 10 times per hour... Most filters rated "up to 75 gal" are less than half of this...

I have some tanks filtering their water at 17 times per gallon...

We can eventually hit a point where the extra filters aren't helping the tank but are costing us more for electricity and media though...

All in all, the less work you want to do the more filtration you add... positioning the intakes and returns logically can also make a big difference.


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## Joea (May 25, 2004)

You can't have too much filtration but you can have too much water flow. Generally smaller tanks will have smaller fish that may have a more difficult time with strong current. Filter ratings are often much more ambitious than they actually are. A filter rated for 150 gallons would likely be just perfect for a 75 gallon.


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## aritg3 (Feb 18, 2008)

So how do you figure out the math? How do you figure out how many times the water gets filtered each our? In other words if I take a bigger filter and put it on a small tank will that filter the water more times per hour than putting that same filter on a larger tank?

Bottom line is I have a 75gal tank. How do I figure out what I should have on may tank to actually filter the water 10 times an hour?

-Ari


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## jayiw (Jan 16, 2008)

aritg3 said:


> So how do you figure out the math? How do you figure out how many times the water gets filtered each our? In other words if I take a bigger filter and put it on a small tank will that filter the water more times per hour than putting that same filter on a larger tank?
> 
> Bottom line is I have a 75gal tank. How do I figure out what I should have on may tank to actually filter the water 10 times an hour?
> 
> -Ari


It's easy:
75 x 10 = 750/GPH.
It does not have to be exact or anything. You could have 2 Marineland c360's which is 360 x 2 = 720/gph which is fine. Or you can have a c360 and say an Aquaclear 110 which is 360 + 500 = 860/gph. With a tank that size I would go with a strong Canister and a strong HOB. Heavy flow won't be any issue with a tank of that size. Flow can be an issue with smaller tanks so with smaller tanks I would not go too much higher then 10x but with larger you can go much more which is always better. Also keep in mind that the said flow rate is mostly exaggerated by the manufacturer. Another thing is as the filter ages the flow rate will decrease slightly. Oh and most especially the more media/the more heavy media, and the older the filter media is will decrease flow.

Jay


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## aritg3 (Feb 18, 2008)

Any reason a canister + a HOB is better than just two canisters? I like the canisters because they are softer and less visually obstructive.
-Ari


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## LG0815 (Aug 1, 2007)

heck no i have a 55 gallon with a 600 gph wet dry filter and a undergrvel filterwith two power heads with 450 gph each


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## stslimited84 (Oct 5, 2007)

I just took off the FX5 I put on my 75 gal this weekend. I already had a XP3 and a rio 2100 powering my UGJ's. With the FX5 there was just too much flow for the juvenile fish too handle.


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## kornphlake (Feb 12, 2004)

I'm not sure where the idea of 10x turnover comes from, I've never seen anybody actually test lower flow rates and show that bio-filtration is affected. How long does water need to be in contact with bacteria for ammonia or nitrite to be consumed? I'm sure there is a certain threshold where if there isn't enough circulation then wastes will accumulate faster than water is passed over bacteria, but I'm not sure if that's as high as 10x turnover as suggested. Bacteria isn't just in the filter, it's on the glass, in the gravel, on plastic plants... it's everywhere water is in an aquarium. If there is circulation in the tank from fish movement, hot water rising from the heater, a bubbler or a powerhead then some of the waste will be consumed by bacteria outside the filter. One could argue that with a larger tank there is more surface area for bacteria to colonize so a smaller filter is needed but more circulation within the tank.

I've been searching for a couple years for some kind of scientific study that proves or disproves the necessity for 10x turnover for bio-filtration and haven't found anything. I recently found a book called "Aquatic Systems Engineering: Devices and How They Function" that looked promising from the table of contents, unfortunately the section on flow rates that contained calculations were all based on UV sterilization, it didn't have anything about flow rates for bio-filtration. The book was very complete otherwise, there were empirical calculations for determining the size pump needed for all kinds of equpment from protein skimmers to chillers but not much for bio filtration. It is the first time I've ever seen calculations to determine the amount of filtration needed based on mathematical relations, yes the book did contain some Calculus to prove the equations but they were broken down so that anyone with a good background in algebra could use them.

Perhaps in terms of mechanical filtration only 10x would be a good place to start for a larger tank. Because a certain percentage of the water discharged from the filter will re-enter the fillter it would take several times turnover to guarantee every particle in the water had passed through the filter in an hour, for this type of filtration calculations could be made. People automatically assume this is true for bio filtration as well, which may not be true, nobody has ever tested it. How much of the waste in your tank is actually particulate waste that needs mechanical filtration? In my tanks I'm not very concerned about solid wastes as I siphon them out during weekly water changes, my primary concern is biological wastes.

Until I can prove it myself I have a hard time recommending 10x turnover to anyone as it seems like an arbitrary number.

To adress the OPs question, can you have too much filtration? I doubt it, you could have too much current, that would be the point where your fish aren't able to swim comfortably against the current. How much filtration is enough and how much is overkill is difficult to estimate as there isn't really any research to reference.


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## niccomau (Oct 14, 2008)

I was having issues with how much is enough. I can get a filter combo that gets me 9.3x turnover rate. If I try to get a higher turnover I always end being between 13-15x. I dunno... I understand that cichlids are messy, but it still seems like 9x turnover should be suffiecient on a 46 gallon bow. I've got a Penguin 350 and I had another Penguin 100 with it. I'm getting rid of the 100 because its a piece of ****!


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## atomicluck (Mar 26, 2009)

The endless question. How much is to little vs how much is to much.

I just changed an Ehiem 2213 (rated up to 66 gallons, output 116 gph & filter circulation 106gph) for a Rena-XP2 (rated up to 75 gallons, max circulation 300 gph) all on a 30 gallon tank. My cichlid's are large 4"-6" and get the thing dirty. I needed something with a lot of output, but had a hard time deciding on what to get.

Been having troubles with the new XP-2, it's weak output and now I'm thinking of exchanging it for another Eheim or something bigger. Then the question comes up how much do I need?

With all the Mom & Pop shops closed in my area now I'm left with only big chain outlets that don't know anything. Even on here there's no real common thought on what way to go.

Do you get double what you need or triple?


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## Toby_H (Apr 15, 2005)

kornphlake,

I cannot argue any of your logic as it is all very sound... but to elaborate as to how I have come to my (current) conclusion...

I fully understand that if we had a typical canister filter meant/designed to function with a 350 gph pump... but we put a 2400 gph pump on it... it is possible or likely that the water will move through the media too fast for the bacteria to consume the waste (ammonia/nitrite)... but when we suggest high turn over rates we are suggesting it is accomplished by adding additional filters, not upping the flow rates of standard ones...

I've personally found that adequate bio-filtration can be achieved with very low flow rates. Basically as long as it is enough to keep any areas from being stagnant. This is, as you explained, because there is beneficial bacteria forming on all the surfaces of the system, not just inside the filter.

I personally recommend "10 x turnover" and feel comfortable doing so much more as a means of "proper" mechanical filtration than bio or chem. At the same time I recommend filter placement to push waste/debris out from under decor which makes it MUCH easier to do a thorough cleaning when we do our weekly water changes as well as increasing the amount of waste/debris picked up by the filters. "Out of sight, out of mind" is a dangerous reality for most of us.

Again kornphlake, I am not challenging nor even disagreeing with anything you said in your previous post... on the contrary I agree with it completely. Yet aside from or in addition to those thoughts... the above is why I do & suggest what I do & suggest...

PS - The â€œup to XXX gallon tankâ€


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## JWerner2 (Jul 7, 2008)

Here is the problem. Without more current you will not get more filtration. I hate seeing my fish get slammed all around cause of this and I doubt they like it much either. Stick with the basic requirements. There is no reason to add so much flow. Flow for biological filtration should be slow from what I have always been told. Bio filtering bacteria likes to be in slower conditions. High flow rates with filtration does the job only for mechanical.

Do the water changes needed to keep the substrate clean along with nitrates down and with a filter designed for your tank you should be fine!



> PS - The â€œup to XXX gallon tankâ€


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## Toby_H (Apr 15, 2005)

JW... I have always appreciated you and generally respect your views... yet I do have to disagree with you on this one. The Aqua Clear 110 is rated for "up to 110 gallons"... I simply do not agree that this filter would be sufficient for a 48" x 18" @ 30" tall tank that is decorated to supply Cichlids with caves/territories. It would allow dead spots in any densely decorated areas and would not create nearly enough current at the bottom of the tank to move the larger waste produced by Cichlids commonly kept in such tanks.

It would be bare bones minimum for the same tank stocked with Tetras or the like with only some long/tall plastic plants as decor...

Then to say "High flow rates with filtration does the job only for mechanical." I also have to strongly disagree with. High flow rates add mechanical filtration to the list of accomplishments of the filter. Using filters that have high out put have performed bio-filtration in my tanks just fine for many years. Both mine and kornphlakes posts above share an elaborated view on this.

Again, not being argumentative, just sharing a friendly opposing view.


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## atomicluck (Mar 26, 2009)

Toby_H said:


> PS - The â€œup to XXX gallon tankâ€


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