# Eliminating water changes for a big tank?...



## gbin (Jun 11, 2012)

My wife doesn't yet know it  , but the 90-gallon bowfront I'm currently setting up in our master bedroom is partly meant to ease her into the idea of big aquariums. We've a major remodel of our living room coming up and I fully intend to put a standard 300-gallon tank (8 ft lone - woo hoo!) along one wall. Tanganyikan, of course.

The subject of this post: We'll be doing a major remodel of the bathroom on the other side of that wall at the same time, and if possible I'd like to take advantage of that fact to plumb the tank such that conventional water changes will never be needed. We've our own well, and except for the temperature (52 °F) the water looks pretty good for Tangs coming right out of the ground; after a bit of aeration (the only way I've tested it), I found pH = 8.0, KH = 214.8 ppm, GH = 286.4 ppm, conductivity 502 µS/cm, nitrate 5 ppm, phosphate 0.0 ppm, and I already knew that there's little or no iron. For our household use (including drinking) the only filtration we use is for sediment. I'm very pleased!

But I'm also still very ignorant! So ignorant, in fact, that I couldn't even figure out good search strings to use to look here and elsewhere online for a primer on setting up a tank in this fashion. At this point I really have no clear idea but only questions: How do you determine what flow rate needs to feed the tank to maintain excellent water quality? Do you need to preheat the water, or do you count on it being a low enough inflow rate that providing ample heating power in the tank itself - combined of course with all the water in the tank that's already been heated (especially in a big tank) - will maintain a stable, preferred temperature (say, in the vicinity of 78 °F)? Similarly, do you need to pre-aerate the water? Obviously the outflow needs to match the inflow minus evaporation... or does it? That is, how does one avoid mineral build-up in the tank when relying on a hard-water source? What is a desirable plumbing layout, and what are plumbing mistakes (or not-quite mistakes) to avoid?...

I'd love to hear from folks with experience doing this kind of thing, or better yet expertise in it. I'd very happily welcome simply being pointed toward resources to improve my education on this subject before bothering you fine folks more about it, too. :wink:

As always, with many thanks!

Gerry


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## DJRansome (Oct 29, 2005)

Take a look at the Cichlid-forum Library in the DIY section for articles about automatic water changing systems.


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## gbin (Jun 11, 2012)

Thanks, DJR! I had looked in the Library but not in the DIY section. (D'oh!) I'll give the material there a read ASAP.

Gerry


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## gbin (Jun 11, 2012)

OK, I just read the two automatic water changing system articles in the Library. They were informative and appreciated, to be sure, but...

They didn't answer any of the (what I figure are pretty preliminary) questions I asked above, at least not as I understood them. So I'm back to asking here for advice from experienced or expert folks, or for directions to any other primers on these systems that people here might know about. What I really need, I guess, is something that thoroughly addresses THE BASICS of this subject instead of/in addition to providing nuts-and-bolts descriptions of how this or that person has put one together. You know what I mean?

Thanks again!

Gerry


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## wryan (Dec 6, 2015)

I am not an expert nor do I have experience, but I'll offer what meager knowledge I can:

1. If you wanted to change out the entirety of the water in the tank over a week you would have to swap out roughly 1.785 gallons per hour (assumes nothing but water in the tank, no furniture, substrate, or technical equipment, 300/168 = 1.785 gph)

2. Irrigation drip emitters are available in various flow rates.

3. With the tank drilled and a bulkhead fitting installed, an overflow can be made up from pvc piping and an 90 degree elbow that when set to your desired water level, allows excess water to flow out of the tank into a drain ... essentially acting as a surface skimmer.

4. There should be two overflows installed, with one set slightly higher - to provide for an emergency back up if for some reason the primary overflow becomes restricted or clogs.

5. At the rate I mention above, you could probably just add the (cold) water straight, allowing the tank heater pick up and handle the temp difference. If you wanted to get real sophisticated, you could add a water tempering valve that mixes hot and cold water to a specific temperature and use that as the supply. Such valves run around $50 to $120, depending on where you source them.


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## DJRansome (Oct 29, 2005)

Sorry, I thought I found this in the Library, but I can't find it now. This helped me:

www.fmueller.com > aquaristic > frontosa > technology > continuous automatic water change system

Frank Mueller is a moderator on Cichlid-forum. I think some of the other tanks have CAWC as well.


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## BC in SK (Aug 11, 2012)

wryan said:


> 1. If you wanted to change out the entirety of the water in the tank over a week you would have to swap out roughly 1.785 gallons per hour (assumes nothing but water in the tank, no furniture, substrate, or technical equipment, 300/168 = 1.785 gph)


No, that would not be comparable to a 100% water change. Not at all.
Since it is a continuous dilution, the water being removed is always a certain % of the new water just put in the tank. It would be difficult to calculate but just a couple examples: Two 50% water changes performed right after each other equals a 75% water change (since only 1/2 the water in the 2nd water change is 'old' water). Four 25% water changes performed one after the other equals about one 69% water change. And 0.5 % water change every hour is far, far less.
I think you would need to go higher then this rate to prevent nitrate creep over time in a heavily stocked cichlid tank.. Unless you want to resort back to doing water changes as well (that is what I did when I ran a drip system, from a round 2003- 2007).
Likely, you'll need 3-4 gal an hour. Start with less. Monitor it. And have it adjustable so you can increase it, if nitrates end up high over time.


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## wryan (Dec 6, 2015)

BC in SK said:


> No, that would not be comparable to a 100% water change. Not at all.


I guess I did say that it was comparable ... although that wasn't really my intent (narrative butchery on my part  )

I was mainly just throwing some numbers out there to provide an illustrative frame of reference.



BC in SK said:


> Since it is a continuous dilution, the water being removed is always a certain % of the new water just put in the tank. It would be difficult to calculate but just a couple examples: Two 50% water changes performed right after each other equals a 75% water change (since only 1/2 the water in the 2nd water change is 'old' water). Four 25% water changes performed one after the other equals about one 69% water change. And 0.5 % water change every hour is far, far less.


That is a valid observation and a very fair point ... :thumb:



BC in SK said:


> I think you would need to go higher then this rate to prevent nitrate creep over time in a heavily stocked cichlid tank.. Unless you want to resort back to doing water changes as well (that is what I did when I ran a drip system, from a round 2003- 2007).
> Likely, you'll need 3-4 gal an hour. Start with less. Monitor it. And have it adjustable so you can increase it, if nitrates end up high over time.


Interesting.

What was your target nitrate level ?

Were you experiencing nitrate creep, using the flow rate you were using at the time ?


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## BC in SK (Aug 11, 2012)

wryan said:


> What was your target nitrate level ?
> 
> Were you experiencing nitrate creep, using the flow rate you were using at the time ?


Well, my experience is a bit of a long story.
My drip system was a very simple, crude system
The body of water was similar to the OP's (180 gal. + 100 gal. both on the same sump that had about 20 gal. in it, so a 300 gal. system). An overflow on the sump. Unfinished basement so I ran a garden hose hooked up to the hot water with a y on it from the washing machine tap. Off the hot water made more sense to me as it is cheaper to heat water with a water heater then an aquarium heater. Essentially the system was a valve that was not shut quite tight so it dripped. Bear in mind, I also did aquaponics during this time, so that would have used some Nitrogen. Just the one tomato plant in the sump but used a fair amount of power (400 watt metal halide and 150 watt HPS on for well over 12 hours a day). Discovered that Tomato plants are not annuals kept in doors :lol: It's trunk was the size of a small tree and when i trimmed vegetation I hauled it out in a number of packed 5 gaL. pales! Also opened the window slightly and had the plant growing partially outdoors, as well. (blocked off the rest of the slightly opened window with a piece of wood).
Sometimes around April 2005, less then 2 years with a drip and aquaponic system I discovered I had 50-60 ppm of Nitrate. Put a 1 gal. pail where the excess water drained and timed it's fill. Less then 40 minutes so a little over 1 1/2 gal per hour. I started to fiddle with the flow rate trying to turn it up. I come home and see that it was coming out way too much and turned it down only to find it was back to the old rate. Once I opened the valve a little, the water pressure must have continued to move the valve more open. My crude system didn't allow for adjusting to a higher rate. Anyways, one day while i was fiddling with the rates I came home to a cooked 180 gal. The water input was hooked on the 180 gal. and shortly before this disaster, the pump in my sump for the 100 gal. had went so i was temporarily using a really small pump for the 100 gal. (and that saved the 100 gal. from the 100 f temps). No lie, a few days before this disaster happened, I was considering getting rid of certain fish.2 oscars and 2 JD and maybe 1 female sal. The fish I was going to get rid of are the only ones that survived in the 180 gal.!
So you think I'm done with a drip system? Nope. :lol: If I can't get a higher flow rate out of one.....I can run another off the cold water and get double with 2. Less then 20 minutes to fill a 1 gal pale so a rate of over 3 gal. per hour. Not so long after, I still had 30+ ppm nitrate so I resumed weekly 25% water changes in addition. When I moved in 2007, I discontinued both the drip system and aquaponics.


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## wryan (Dec 6, 2015)

BC,

Interesting story ... thanks for sharing it ... :thumb:

Just curious on the tomato plant: How long did it stay productive and produce ? (We like tomatos here ...  )

On the amount of water required, I imagine there are a number of variables that could play into it, that could dictate whether or not one experiences nitrate creep in a particular scenario.

Interestingly, fmueller's site which DJ linked, states that he was running about 30 gallons per day on a 240 gallon "Frontosa" tank. Looking at the species list he was keeping, it appears as though there was a fairly significant number of fish in the tank ... although I didn't dig deep enough to get the counts on all the species.


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## gbin (Jun 11, 2012)

Thanks for the helpful advice! Between you folks and what I am turning up online (my searching is getting more productive the more I learn, of course), I believe I'm starting to understand this subject.

In the preceding discussion, it seems to me that the dilution effect of changing smaller amounts of water more frequently is being overestimated by quite a bit. I'm not questioning your straightforward math, BC, but the fact is that no person/system WOULD perform X number of water changes one right after another; in a continuous water changing system, time is obviously passing and that needs to be factored in. In my reading it seems to me that this dilution effect is actually often overestimated in discussions such as this one, making larger water changes appear more important than they are. Probably the best source I've found for treating this matter is here: http://reefkeeping.com/issues/2005-10/rhf/index.php.

For example (if I understand things in that linked article correctly), doing a single water change of 168 gallons for a 300-gallon tank each week would amount to a 56% water change per week. Doing 7 water changes of 24 gallons each day (= 168 gallons in a week) would instead amount to a 1 - (0.92)7[/super] = 44.2% water change per week. And changing 1 gallon every hour (= 168 gallons in a week) would amount to a 1 - (0.99667)[super]168 = 42.9% water change per week. I can't do the math for truly continuous water-changing (I've always hated calculus), but you get the point; it's still going to be solidly above 40% per week. There's a meaningful reduction in water-change efficiency with more, smaller changes involved, certainly, but there's also still a meaningful amount of water being changed.

So unless the aquarium is really overloaded, which people (including me) don't tend to do with Tangs, having an automatic water changing system flow rate of 3-4 gallons/hour seems like overkill. I can't imagine nitrate-(and other pollutant-)creep being a problem with a 1 gallon/hour flow rate (= > 40% weekly water change) as outlined above.

If anyone sees how I've gotten this wrong, please don't hesitate to point it out to me!

I can see now, too, that there's no real cause for concern over the temperature and oxygen level of the water coming in, as the inflow rate would be low enough compared to the total water capacity of the tank that the heater and filter system should have no trouble maintaining stability.

I still don't know about the build-up of minerals from the use of hard water and the occurrence of evaporation, though. Maybe the answer to this question is in that linked article as well, and I just need to read it again with revised focus to grasp it. I'll give that a try.

Gerry


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## BC in SK (Aug 11, 2012)

gbin said:


> can't imagine nitrate-(and other pollutant-)creep being a problem with a 1 gallon/hour flow rate (= > 40% weekly water change) as outlined above.


Well, my advice is to start there ...and have it adjustable to a higher rate in case it does not. Of coarse starting out with younger small fish, it may very well do the trick to begin with.
I'm not convinced it would equal a 40% water change. The longer the time span, the greater amount of Nitrogen is released from respiration and fish waste (of course originating from the amount of food put into the tank). So I don't see time passing as some how making numerous small water changes more effective. 
I guess there are other ways of looking at it. Just an example: Suppose 20 ppm of nitrate. 24 gallon a day replaced on a 300 gal. system should remove about 1.6 ppm nitrate (not factoring in any dilution effect of continuous water changing). If that is what your fish produce (11.2 ppm nitrate a week) from respiration and break down of fish waste, then the 20 ppm nitrate will be maintained. If they produce more then 11.2 ppm a week, then you will get nitrate creep. 
I think what also needs to be considered is the ways and methods of how many aquarists will do a typical water change. Fish waste is physically removed. No such thing is happening with most automatic systems so there is a greater build up of fish waste over time. I think this also needs to be considered when thinking over the longer term.


wryan said:


> Just curious on the tomato plant: How long did it stay productive and produce ? (We like tomatos here ...  )


Well the plant grew like crazy but did not produce. It flowered and I got 1 tomato out of it :lol: The flowers fell off. For many years after, I suspected pH 8 water as some how affecting phosphate up take and this somehow causing the flowers to fall off. A few years back, in a thread on aquaponics some one suggested that I would have needed insects to pollinate or do it myself manually with a small brush. I did however, start over 100 plants from cuttings. Gave most of them away but also had many in my garden. Big beefsteak variety, they produced well out doors. 
That tomato plant I had about 2 1/2 years. Not too long after my hot water disaster, I cleaned out my sump. I needed to address my nitrate issue. I know tomato plants are water loving, but it really surprised me how this plant rooted the entire tub of the sump  So the majority of the roots were entirely submersed in water! I destroyed too much of the roots, and the tomato plant did not survive very long, after the sump cleaning. After that, i grew a hot banana plant. It was a good sized bush, but nothing even close in size to the tomato plant. I got a few hot bannana peppers out of it, but not a lot.


wryan said:


> Interestingly, fmueller's site which DJ linked, states that he was running about 30 gallons per day on a 240 gallon "Frontosa" tank. Looking at the species list he was keeping, it appears as though there was a fairly significant number of fish in the tank ... although I didn't dig deep enough to get the counts on all the species.


Well, that would be about 1.25 gal/hr. Frontosa are big fish as well. Maybe that is a better comparable for gbin then my situation with Oscars and CA.


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## Ivan Macko (Sep 10, 2017)

Hi guys. Interesting reading here. I started a water temp oscilation topic for AWC just few days ago too...

I set up my system differently. I have a 13ft, 1100l malawi tank. Two FX6. Drilled tank with an overflow.

My system of AWC consists of : - three 10" regular pre-filters removing chlorine and general impurity from tap water
-programmable magnetic water valve
-system of automatic dosing pump for trace elements and any other supportive/benneficial chemistry in future

My aquarium just finished fishless cycling after 7 weeks. I've let it with 0 water changes the first month. Now it was getting 200l of new water every day, which removed all the nitrates after cycling. Switching to 100l per day since now on.

My problem with this setup is that those water quantities being changed are not preheated. Only cold water. I screwed it up little bit here. Next time I would prepare hot water source in technical Room as well! That is my advice here maybe... Anyway not a problem if Your plan a continuous drip system.


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## gbin (Jun 11, 2012)

You're right, BC, unless I manage to do especially well setting up the filter intake(s) I'll have to plan on syphoning the solid waste produced by the fish at least once in a while.

It sounds like an awesome tank and great system, Ivan! Too bad you're wasting it on Malawi! :wink:

I won't be preheating, either, and the water comes out of our well pretty cold. (In fact I won't be pre-anything the water, as it fortunately looks to be good for Tanganyikans the way it comes out of the ground - except for temperature.) I'm hoping that with only changing 8% per day via continual replacement the tank's heater(s) will be able to keep the water at a desirable and stable temperature, as you said, but I'm not entirely certain. You're doing about 9% replacement per day all at once? Have you tracked temperature through time in your system? Maybe I should take a look at your thread...

Gerry


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## gbin (Jun 11, 2012)

I just read through your thread, Ivan. Your temperature fluctuation doesn't sound very bad, really; if it only happened once in a while I think the fish would handle it fine, but having it happen daily does sound like a bit much for the fish to deal with. I like DJRansome's suggestion to switch to more or less continuous rather than episodic water replacement. As discussed in this thread, I don't think that would really result in too much reduction in water change efficiency.

Gerry


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## Ivan Macko (Sep 10, 2017)

I was just rethinking the whole thing, I thing You are right. Will be switching to continuous drip as well. I will make a single manuál water change as the waste builds Up, hopefully just not that often aa I travel alot...

Hehe why do u think malawi is not do good? Dont have the fish yet  any advice apprexiated


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## DJRansome (Oct 29, 2005)

Malawi will do great, gbin is just a fan of Tanganyikans.


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## Ivan Macko (Sep 10, 2017)

So anyway, it was very useful spending some time here on this forum, as always  hopefully I will be able to share with You guys my new aquarium shortly, we should bring the fish in at the end of this month. Maybe it will also be helpful for others, especially seeing possible mistakes that I made and what could be done better 

See u later!


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## gbin (Jun 11, 2012)

Yes, I was just joking, Ivan. I like Tanganyika more, but Malawi will make a fun tank, too! :thumb:

And I agree, this forum is great!

Gerry


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## Ivan Macko (Sep 10, 2017)

Btw guys, talking about regular water changes- although I run new tap water through prefilters, it reads 0 on chlorine, but I get around 10+ ppm od nitrates out of my pipes :/ maybe I am opening an already solved topic, but how about utilising slow flow of a continuous water drip system and build in some anaerobic-bacteria filter stage?Maybe just by filling last 10" filter with matrix or at least lava stone? Or is there any other way of getting rid of the tap-water nitrates?


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## Narwhal72 (Sep 26, 2006)

I am a little late to this conversation, but if anyone is interested there is a mathematical formula for calculating your water change rate.

T=9.2(v/f) This formula is used to calculate the turnover rate of a container where filtered and unfiltered water are mixed. It can be used for calculating turnover rate of a filter or in this case, exchange rate of a continuous drip system.

T= time in hours
9.2 is the purity coefficient (equal to 99.99% of the tank volume) 
V is the volume of the aquarium
f is the flow rate.

If the flow rate of the drip system was 1 gallon per hour then plugging that into the equation we would get T = 2760 hours (115 days) to get one 100% water change.

If we want to work backwards to determine flow rate based on a 50% water change per week we would get 168= 9.2(150/f). f comes out to 8.215 gallons per hour.

Just in case you were still wondering.

Andy


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## wryan (Dec 6, 2015)

gbin said:


> You're right, BC, unless I manage to do especially well setting up the filter intake(s) I'll have to plan on syphoning the solid waste produced by the fish at least once in a while.


FWIW, You could set up the filter intake plumbing with a capped tee in it - so that you could uncap it and attach the hose you plan to use to vacuum the solid waste and just suck it into the filter.

Just a thought.


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## gbin (Jun 11, 2012)

Andy, what's the source for your formula? It appears to disagree with what I linked above.

Great suggestion, BC! :thumb:

Gerry


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## BC in SK (Aug 11, 2012)

gbin said:


> It appears to disagree with what I linked above.


Yes it does not agree with your formula. 
This link agrees with your math:http://www.angelfish.net/DripSystemcalc.php I plugged the numbers in and get 43% water change weekly on a 300 gal system with 1 gal. per hour (24 gal. per day).
Not sure Narwhal has the right formula to calculate water change rate (??). His formula is about how quickly water is mixed. I think we are trying to determine the make up of the water that is being removed. How well the new water is mixed has little to do with the flow rate of the new water, but rather the combined flow rate of the filters/power heads/circulating pumps.
I think my hot water disaster sort of demonstrates. When the valve opened up, I probably had a flow rate of 20-30 gal./hr of hot water. Took a number of hours to raise the temperature in a 180 gal. to over 100* f but because I was temporarily using a tiny pump (100 gph) in my sump for the 100 gal., that tank only got to 90* f and was spared.
Now, if gbin's math (and my link) is correct, something else has to explain how I ended up with high nitrates with the rates I was using. Maybe it's fish waste accumulation (??). I don't remember the specific amounts of Nitrate I had to begin with, other then they were very low. Low enough that I had figured there was little point to even bother testing for it. Probably a span of well over a year and almost 2 years of running this set up, I tested for nitrates out of curiosity and was very surprised to find out it was high!


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## gbin (Jun 11, 2012)

Your experience definitely offers a cautionary tale, BC. I appreciate your sharing it!

I reckon there's nothing for it but to feel one's way in - hopefully having planned plenty of adjustability in the system at the the outset. I'd just like to begin with as much foreknowledge as possible.

Gerry


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## gillmanjr (Jan 27, 2017)

I didn't read through this entire thread but I assume it is a discussion about how to build a totally automatic water change system, probably via some kind of drip and makeup method. Personally I wouldn't do that. I would create a sort of "Semi-Automatic" water change system if I was in your position (the OP). Get a thermostatic mixing valve that can be set to about 80F and put it in the wall, connect cold and hot, and run the output either into the filtration return line or directly into the tank with an isolation valve. Then build a drain line from your tank at around 3/4 down the tank level directly to your house drain, again with an easily accessible shutoff valve or two. Then to do a water change all you would have to do is open one valve, wait a couple minutes until the water level in your tank drained down to the drain line, then close that valve and open another and wait until the tank is full. Doing water changes would literally be a matter of opening two valves and then closing them. Thats the way I would do it, though you would still need to be present to "perform" the water changes, if you are trying to avoid that than you need fully automatic. I just don't like the idea because there is too much that can fail and then you end up either with an empty tank and dead fish, or a flooded house.


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## DJRansome (Oct 29, 2005)

The drip system that fmueller describes could not end in an empty tank...maybe there is a risk of overflow if you lose siphon but it would be a slow drip and you could have a water alarm on the surface at risk.

In addition, there is almost no investment or apparatus to fail/repair/replace. Tubing, PVC and a self-piercing valve (like $5 each).


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## Narwhal72 (Sep 26, 2006)

That equation is from the book Aquatics Systems Engineering by P.R. Escobal

The formula is used to determine turnover rate. Not mixing. Turnover rate would be the amount of time it takes to send the volume of the aquarium through the pump, filter, or in this case exchanged with new water coming in.


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## Narwhal72 (Sep 26, 2006)

Looking at the calculator you linked to BC, I really can't tell which one is correct. The link doesn't show the math so I can't tell (and calculus wasn't my strong suit in school anyways). But it does seem to take into account the influx of new water and outflux of old water better over time.

It may be that P.R. Escobal's equation really only applies to filtration and does not translate to water changes very well. Although why it doesn't is not obvious to me.

Andy


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