# Having Trouble Deciding Tank Turnover Volume



## Pablo B. (Aug 3, 2012)

I am having a issue over what type of turnover per hour in volume (theoretically) in resetting up my 75 gallon tank. NOW I am VERY curious as to what total volumes you all run and for what size of tanks? Obviously things have been working well for many of you and for quite a while and I am curious how far off in my thinking and logic I truly am. I some of you would please state your total GPH and tank volume that would be so awesome as well as how long it has been running. I know this sounds like a stupid question but I am seriously stuck on this one and I want to change my set-up asap. Thanks for any replies.


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## BrendanMc (May 30, 2012)

I have a 60 gallon and my two filters combined with media probably run about 500 gph, so that's a turnover of about 8 per hour. It's been running for about 6 months with no problems.


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## metricliman (Sep 3, 2012)

I have a 55 and I'm doing 600 gph. Ideally, you would want over 10x turnover, but 7-10 is fine.


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## Narwhal72 (Sep 26, 2006)

I love it when these questions come up on the forum.

The proper way to calculate turnover in an aquarium is T= 9.2(V/f) where T is the number of hours it takes 99.99% of the tank volume to pass through the filter one time, 9.2 is the purity coefficient, V is the volume of the tank, and f is the flow rate.

The reason for this calculation is because we are all mixing filtered and unfiltered water in the same container. Some of the water will inevitably pass through the filter multiple times before some water even goes through once.

A good rule of thumb would be at least one turnover every 2 hours or about 12x per day.

So if we work it backwards and figure the net volume of the 75 gallon tank at 65 gallons:

2 = 9.2(65/f)
0.217 = 65/f
f x 0.217 = 65
f = 299.54 gallons per hour

So about 300 gallons per hour. Of course more is always better.

Andy


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## Dawg2012 (May 10, 2012)

That makes sense however how do you, in general, account for the often times gross overrepresentation of actual flow that almost every filter manufacturer makes? I think that factors heavily into the 7-10x turnover 'rule of thumb' (not that I agree or disagree with it - see below).

We also need to account for mechanical filtration, as I believe turnover recommendations are determined largely based on biological considerations. You can have great turnover/flow/whatever - but if it's all biological then you will benefit from additional mechanical.

Flow is also an important consideration in keeping particulate matter suspended in the water column until it can be picked up by an intake. Of course placement and tank layout affect this, it's just another aspect of turnover that needs to be considered if you are relying solely on turnover for flow.

I run an FX5 on my 75 gallon tanks and they work great. They are more than adequate for biological, and from a mechanical perspective do a good job - though I do run filter pads in the top chamber as the stock foam pads don't seem to... honestly... do much.

I used to run smaller canisters on them that were rated for the tank size and while they handled the biological just fine, I found greater flow and/or a stand alone HOB for additional mechanical to be very effective not only in water clarification but keeping matter suspended until it was picked up by either filter as well.

So... I would recommend more an approach to filtration rather than hard numbers. Use turnover as a gross estimate for biological requirements, taking into account under/over stocking, but realize that mechanically you may need more and/or a different filter to keep the water clarity good.

There's no single right answer - but you found the right place to get lots of opinions which will help you determine what works best for you.


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## Pablo B. (Aug 3, 2012)

Okay.....thanks for the quick responses! This is what I am debating over. Right now I have 1504gph in the system and it seems to be working VERY well, according to cleanings, water testings, fish health, etc. What I wanted to do was to get RID of the three Fluval 205's that I have under my cabinet and use ONE canister. Right now, the "numbers" would say that the three 205's would be putting out 540gph.......NOW I KNOW that this isn't real life numbers but I wanted to get something that would hold it's own and I think I found that in the Eheim 2075 Pro3 canister filter. My initial set-up now was to ditch the Emperor 400. the Aquaclear 70, and the Fluval C4 and add two Aquaclear 110's loaded with Seacheam Matrix as well as having the Eheim loaded with the BB out of the three 205's that are already "matured". That would leave me at 1,330gph (probably tested without a full lot of media, etc) so it would be a tad lower. Am I worrying about something I shouldn't even be concerned with here??? The Eheim says it can handle a tank up to 160 gallons and I am only a 75 gallon. I am thinking that I will be fine but I need to hear it from other people's writings here if I am right or wrong or if I am indeed crazy! 

I look to all the 'experts' here to chime in and please help with their opinions. I just don't want to take steps backwards BUT I hate having three canisters underneath my cabinet and all the hoses everywhere. Just want to clean it up and maybe get a better canister in the process.

Thanks to Andy for your scientific approach/reply as well! Much appreciated! :thumb:


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## Pablo B. (Aug 3, 2012)

I wanted to initially over filtrate because I have had a few tanks before in the past where I didn't have enough filtration and bad things happened. I didn't know better back in the early nineties, but I knew that this time around I wanted to make sure I was 'taken care of' in the filter department, and maybe I went a little overboard, but like I said, it seems to be working very well and I don't mind all the maintenance it takes working between all of the filters at different times. Gives me something to do and more hands on with my project/tank as well.


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## Dawg2012 (May 10, 2012)

I think from a biological perspective you will be fine... In fact I think from all perspectives you will be fine.

I know you are going to load the Eheim with media from the 205's and this is great. :thumb: At the same time I'd be cautious of other major changes... ALL your current media, including substrate, is balanced with your bioload, so while your 205's have a lot of media, your other filters ARE carrying part of the load. If you can swap any other media, or leave one or two of the others on until the Aquaclear's populate, that would be an added measure of safety... as would not increasing stock for a few weeks and possibly feeding a little less. I've learned over time to be conservative as this helps alleviate those times when... overconfidence bites me in the rear lol.


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## B.Roberson (Nov 6, 2011)

can i ask a complicated question to these answers? 
I have a 75 gal and a 38. But only 1 ac 70 on my 38. but my 75 have a ac110, and an xp3.
now alone, ac110 is 500 gph ,no media.xp3 is 300
with media HOW DOES ANYONE KNOW?
do you take out the out put into a huge bucket or container and measure what coming out after media,and what if media is dirty? i dont see how you can measure that output? 
I would love a scientific and realistic answer. thnx


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## Pablo B. (Aug 3, 2012)

Bob/Brian/Brett......I don't think anyone knows the EXACT answers to what the exact flow/gph is with media inside of it, and I am sure you just chop off about 100gph to 300gph depending on which filter it is internally design-wise (like the recenly debated FX5) and I know that my 205's aren't putting out anywhere's near 180gph. Maybe 80-100? As far as the Aquaclear 110 pushing 500, I would tend to believe with half a sponge (cut for media room) and using the Seachem Matrix as much as possible, and maybe using the othe half of the sponge atop the media, it's got to not lose THAT much gph......maybe 100? Unless you scientifically have a way of testing every condition with different hose lengths, there could be a multitude of answers to your question.

This is purely why I like to overfiltrate on my tanks now. Because of THAT. The unknown. I figure if the Eheim 2075 is good to run a 160 gallon tank, it MUST be great enough with it's internal design to handle my measly 75 gallon tank with NINE fish in it. That's right.....nine. All are a good 5 to 7 inches but I want them to have the healthiest conditions I can provide for them for longer life and happy life.

It'a almost like a guessing game of sorts because you really never know what the TRUE output is on a given filter loaded up with all the different types of media and floss and **** that they have out there, soooooo..........I guess this is where the "namebrands" come into play like Eheim that are tried and trued and others like Fluval the same. Don't know much about Aquatop or SunSun so I cannot speak a word for them but i CAN say the in my book and thoughout my life.......you end up getting what you pay for. There is no magical deals or super steals so to speak IMO. Yeah.....you can get the stuff for cheaper on Ebay BUT I personally wouldn't feel all too comfortable spending $60 on a canister filter with supposedly all these bells and whistles. I have been in the automotive business for 22 years and you get what you pay for AND there is a reason WHY Porsche, Audi, MB, BMW parts cost more than a Toyota corolla. All in the design of the car and how it's made. If you want a KIa......nothing wrong with that. I just want an Eheim filter for once as I have used Fluval for years and I want to pay the price for what I really believe is the quality and worksmanship in the piece.


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## Narwhal72 (Sep 26, 2006)

There actually is a way to measure it but it takes some special equipment and a second person. I have done it many times in the lab.

I had several specially built aquariums made that are divided in half with a solid glass divider. On one side I put graduations for every gallon on the aquarium.

Then I fill the other side to the top of the divider. I put the inlet for the filter on the filled side. A hose from the sink goes into that side in order to maintain a constant water level on that side. Then I start the filter up. I ignore the first gallon as it takes a little bit to adjust the water flow to maintain the constant level. Then my assistant uses a stop watch to mark how long it takes to fill each gallon. We use a 29 gallon tank for most medium sized filters and can take about 10 readings in a shot. Then we repeat it twice more for a total of 30 readings which we then average to determine the flow rate.

I have done this with a variety of filters but I can only comment on the Aqueon filters which is how we determine their flow rate. We feel this is more accurate than hooking the pump assembly up to a flow meter.

Andy


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## B.Roberson (Nov 6, 2011)

you answered it for me B Pablo. Thanx, its just about making sure you have ENOUGH filtration to keep your fish healthy and happy
i guess we could all get scientific and all and go overboard,my theory is WC and regular cleaning and my fish have been fine. I love reading everyones inputs though,there is so much to learn......


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## nodima (Oct 3, 2002)

Narwhal72 said:


> There actually is a way to measure it but it takes some special equipment and a second person. I have done it many times in the lab.
> 
> I had several specially built aquariums made that are divided in half with a solid glass divider. On one side I put graduations for every gallon on the aquarium.
> 
> ...


With canisters and or sumps, it should be easy enough to simply put the outlet in a 5 gal bucket, and do the timing that way. We don't need to be super precise, but doing the test a couple times should give you a pretty good idea of how each filter is performing.

With HOB's it would take some effort to duplicate this sort of test.

Chasing GPH is only one measure of filtration. The amount of media and the contact time the water takes over it is also important. I've seen others reference studies showing slower rates over larger volumes of media do a better job of filtration. In practice, there has to be a balance between GPH and media volume. Another measure concerns the circulation in the tank which can have an impact on water clarity and "clean substrate". Circulation IMO is as much a function of strategic placement of outlets and type as it is a function of GPH. Good circulation does not always mean higher GPH. Using spraybars or UGJ's is a great way to increase circulation over other outlet types, but does not require bigger GPH to drive it.

One other note - a previous poster brought up Eheims being expensive and relating it to better quality. While there is no doubt my Eheims are much quieter than any of my Fluvals ever were, their biggest advantage IMO is the media capacity relative to their rated GPH. It seems to me that my Eheims are optimized between GPH and media in a way that others are not.

To The OP - going from 3 to 1 is a good idea, though I'd advocate for having at least a pair of filters. This will cover you in case of issues with one, and allows you to do maintenance on one at a time, with less risk of drastically changing water parameters.

FWIW my 75 planted is run by a pair of Eheim ProII 2128s; my 125 is a sump (Mag 12)and an Eheim ProII 2128; my 180 is a sump only (Mag 18). All tanks have been up and running for years in various configurations.


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## Pablo B. (Aug 3, 2012)

Dawg2012 said:


> I think from a biological perspective you will be fine... In fact I think from all perspectives you will be fine.
> 
> I know you are going to load the Eheim with media from the 205's and this is great. :thumb: At the same time I'd be cautious of other major changes... ALL your current media, including substrate, is balanced with your bioload, so while your 205's have a lot of media, your other filters ARE carrying part of the load. If you can swap any other media, or leave one or two of the others on until the Aquaclear's populate, that would be an added measure of safety... as would not increasing stock for a few weeks and possibly feeding a little less. I've learned over time to be conservative as this helps alleviate those times when... overconfidence bites me in the rear lol.


Dawg......I have decided after I load up the Eheim with all of the media from two of the 'biological' Fluval 205's that I have going and after careful measurements, I am going to keep a Fluval C-4 HOB running as well atop while I build up the BB in the AC110's and I was also thinking about using Stability during this process after reading about it in that article about the Eheim 2080 versus the Fluval FX5. How those guys said that they always use Stability when they start a 'new' system. What do you think? I was also thinking about keeping the third one as a 'back-up' unit and a second canister for the 75 gallon even though my main goal was to rid of all of the hoses, I have been thinking hard about IF the Eheim went down temporarily, what would I have running???? Just three HOB's. Sooooo......I thought maybe I should keep one up and running as a biological unit as well for that reason. Full of Matrix. By the time the Matrix cures into some BB, all should be running great. All this moving around and switching things is kind of nerve racking just thinking about it! :-?


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## nodima (Oct 3, 2002)

Pablo B. said:


> <snip>... I have been thinking hard about IF the Eheim went down temporarily, what would I have running???? Just three HOB's. Sooooo......I thought maybe I should keep one up and running as a biological unit as well for that reason. Full of Matrix. By the time the Matrix cures into some BB, all should be running great. All this moving around and switching things is kind of nerve racking just thinking about it! :-?


To each his own, but IMO you are way over thinking this. There is a point where one is simply throwing money away. 3 HOB plus 3 Canisters? Holy Cow. I thought my 75 with 2 Eheim Pro II 2128's was overkill...

Though I can see why you'd want to eliminate some hoses and piping. It must look like a refinery!


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## metricliman (Sep 3, 2012)

I think you guys are all over thinking this. Like I said before, 7-10 times turnover. This rule of thumb accounts for the fact that the 'real' GPH is often far less than the stated GPH. In reality most of us are doing around 3-5 times turnover with media.


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## Pablo B. (Aug 3, 2012)

metricliman said:


> I think you guys are all over thinking this. Like I said before, 7-10 times turnover. This rule of thumb accounts for the fact that the 'real' GPH is often far less than the stated GPH. In reality most of us are doing around 3-5 times turnover with media.


I agree 110% and that is precisely why I wanted to have the amount of filters I had (new arrangement). Just look at what the FX5 lost from what it's "advertised" ratings were. I know that every single filter out there is going to be the exact same so this is why I wanted to have a FEW more than normal to make up for that loss and be in that 7-10 range easily.


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## mrbeadheadful (Oct 24, 2012)

Wow.... A better rule of thumb is to just double what manufactures say... no need for anything else... ****, I had just an AQ70 on my 55 for the longest time.


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## Pablo B. (Aug 3, 2012)

mrbeadheadful said:


> Wow.... A better rule of thumb is to just double what manufactures say... no need for anything else... #%$&, I had just an AQ70 on my 55 for the longest time.


How many and how large of fish did you keep in that 55 gallon tank and how often were you doing water changes? I am using an AQ70 with Seachem matrix as ONE of the HOB's on the 40 gallon dwarf tank that I am throwing together. That and a Fluval C-4 and another AQ50 with Seachem Matrix along with one of three Fluval 205 canisters that I will soon be taking off of my 75 gallon tank in place of an Eheim 2075. Attempting at making the plumbing a little less looking like an octopus down there while getting something I have always wanted.......an Eheim model filter. I will use one of the 205's as a back-up unit I decided since they are already filled with BB and are "seasoned" already.


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## mrbeadheadful (Oct 24, 2012)

When just the AQ70 was on, it had 2x bio max, and 1.5x foam

1 Firemouth (adult female)
1 bolivian ram (adult male)
4 3 spot gouramies (2m 2f adult)
1 rainbow shark
3 platies
1 peacock eel
1 juv green severum (less than 3")
and various other community fish.

Water changes were done via python, and were about 50%-60% every 1.5-2 weeks


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## Pablo B. (Aug 3, 2012)

That explains a lot. That is still pretty **** good, though. With all my water testings including oxygen testings, I can go usually three weeks without a major water change. Whether that has to do with filtration or not, I don't know, but I would sure like to think it has some bearings on it and with all the Seachem Matrix that I use in this tank as well as the Eheim Substrat Pro. The filters stay unusually clean and I guess I don't really over feed the fish as they have two eating schedules a day that they eat. I DO have to top off the water level at times as the evaporation sometimes gets the HOBs making too much noise, but other than that, all is fairing very well. All are healthy and the amount of filtration I use isn't overbearing on them at all. Plus I use a few power heads with spray bars for water flow across the tank from each side to aid in movement.


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## mrbeadheadful (Oct 24, 2012)

Pablo B. said:


> That explains a lot. That is still pretty darn good, though. With all my water testings including oxygen testings, I can go usually three weeks without a major water change. Whether that has to do with filtration or not, I don't know, but I would sure like to think it has some bearings on it and with all the Seachem Matrix that I use in this tank as well as the Eheim Substrat Pro. The filters stay unusually clean and I guess I don't really over feed the fish as they have two eating schedules a day that they eat. I DO have to top off the water level at times as the evaporation sometimes gets the HOBs making too much noise, but other than that, all is fairing very well. All are healthy and the amount of filtration I use isn't overbearing on them at all. Plus I use a few power heads with spray bars for water flow across the tank from each side to aid in movement.


Now on my 125g, I ran an xp3, fluval 404 and fluval 204, very heavily stocked, heavy feedings too.

The filters were all bio/mech media, and water changes were about 50% every 2 weeks as well.

My current 20g has 
~ penguin 150b(with biowheel removed, and supplementary aquaclear sponge)
~whisper 20 with purigen in place of carbon


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## ratbones86 (Jun 29, 2012)

Rule of thumb for filtration = HOB 10x turn over rate Canister 5x turnover rate


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## jonathantc08 (Nov 16, 2012)

Turnover doesn't help and bacteria actually filters better at lower flow rates. The only real thing is how much media you have and how much water you can expose to it.... if all the water in your tank is exposed once/hour and given you have the right amount of media for your size tank then that's all you REALLY need. GPH is another way for marketing teams to pull more money out of your pocket.


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