# water change analysis



## beaslbob (May 29, 2009)

I posted in the freshwater forums my water change analysis for your consideration.

the same exact concepts apply to marine tanks as well.


----------



## Rod4Rodger (Jan 2, 2012)

All true but PH might be different depending on the species. Fresh water can range a long way from Discus to African Cyclids.


----------



## beaslbob (May 29, 2009)

Rod4Rodger said:


> All true but PH might be different depending on the species. Fresh water can range a long way from Discus to African Cyclids.


Actually my Fw are all over 8 on PH.

They deleted my other thread.

But just for conversation here is the bottom line equation:


before water change=replacement water+(change between water change)/(fraction of water changed)

This assumes constant conditions including a constant rate of change and enough water changes have been done so the before water change values are constant.

for example assume you have 30ppm nitrates in the replacement water and nitrates increase 12ppm between water changes and you change 10% (1/10) the water.

Before water change=30ppm+(12ppm)/(1/10)=30ppm+(12*10)=30_120=150ppm

After the change nitrates are 138 and then nitrates rise to 150 before the next change.

my .02


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> Actually my Fw are all over 8 on PH.
> 
> They deleted my other thread.
> 
> ...


Wow, actually intelligent speak and not jumping elephants and flipping giraffes....amazing

Your math only works if your replacement water has nitrates. In all the posts on this site I have seen maybe 5 that deal with this issue. The majority have 0 nitrates in their water.

So with the majority...if your tank has 100ppm nitrates and you change 50%, your nitrates reduce to approx 50ppm. If you watch your feeding and use plants, your nitrates will actually drop below 50ppm after a week has passed or stayed at 50ppm. Do another water change of 50% and they are now say 30ppm. And it continues to go down with each week. To be kept at around 20ppm for the plants on a FW tank at least or the plants suffer.

If your intention is to say that water changes are not good, you are dead wrong and really need to do more reading and stop living in that world you live in. MOST people don't have to deal with the water going in being nearly just as bad or worse than the tank water it is mixing with. In this case there are other ways to mitigate those issues, but not doing water changes because of that issue makes absolutely no sense. You promote your methods and yet, don't show in any type of photos what your tanks look like and the ones you do have in your gallery look like someone has puked in them. Nobody wants that in their livingroom - that, I know for sure. Maybe you would be allowed to bring them inside your own home if they weren't such an eye-sore, but can't speak for your spouse.


----------



## beaslbob (May 29, 2009)

jrman83 said:


> Wow, actually intelligent speak and not jumping elephants and flipping giraffes....amazing


 just trying to keep it light and humorous while emphasizing that the actual (linear) units are not important. 

Hmm wonder how many flipping giraffes are in a galloping elephant


> Your math only works if your replacement water has nitrates. In all the posts on this site I have seen maybe 5 that deal with this issue. The majority have 0 nitrates in their water.


Actually that equation also works with 0 nitrates in the replacment water. In that case:

before=0ppm+12(/1/10)=120ppm. After water change 108 back up to 120 before the next.


> ...
> 
> If your intention is to say that water changes are not good, you are dead wrong and really need to do more reading and stop living in that world you live in.


 that is not my intention. Tanks can and have been maintained through water changes alone. The intention is to precisely analyze exactly how effective water changes are.


> .


Using that equation and say you have a tank that has 5 ppm nitrates before a water change. And you are doing 10% water change every 10 days. With 0 nitrate water. In order for that to happen the tank must be increasing nitrates at .5ppm between water changes. or .05 ppm per day.

As I stated the equation should give people some feel for what is happening in their tanks.


----------



## jrman83 (Jul 9, 2010)

Very few people, at least those I am familiar with in the fw world, do only 10% water changes. Most will do at least 35-50% and some do even more. So the impact to reduce nitrates is greater than your example shows. If after a water change your nitrates only go down 10ppm or even 10% and the value was high to begin with, you didn't do a large enough water change. If the water change is a higher % then the value after one week (when it is time to do the next water change) will not even be back to where it was, it will be lower. This assumes the reason nitrates got high to begin with is the tank is NOT planted, a lack of regular water changes, heavy bio-load, or overfeeding. Once regular maintenance starts or resumes, they can only go down if the issues that created it to begin with are mitigated.


----------



## beaslbob (May 29, 2009)

jrman83 said:


> Very few people, at least those I am familiar with in the fw world, do only 10% water changes. Most will do at least 35-50% and some do even more. So the impact to reduce nitrates is greater than your example shows. If after a water change your nitrates only go down 10ppm or even 10% and the value was high to begin with, you didn't do a large enough water change. If the water change is a higher % then the value after one week (when it is time to do the next water change) will not even be back to where it was, it will be lower. This assumes the reason nitrates got high to begin with is the tank is NOT planted, a lack of regular water changes, heavy bio-load, or overfeeding. Once regular maintenance starts or resumes, they can only go down if the issues that created it to begin with are mitigated.


But your analysis seems to be the transitory effects. The equation reflects the effects of regular maintenance and where the tank conditions finally wind up. With given tank conditions and water changes, the value before the water change is always the same.

For a 1/3 water change you mentioned:

Try a 1/3 water change with 12ppm increase.

before water change= 0ppm+12/(1/3)=36ppm

of course plus whatever is in the replacement water.


To limit nitrates to a 5ppm final value:

5=0+(increase)*3

increase=5/3ppm

So in order to limit the before water change to 5ppm you have to limit the build up between water changes to 5/3ppm.

If your replacement water has more then 5ppm nitrates then the between water change value must decrease instead of increase to consume the nitrates over 5ppm between changes. For example, say the reaplacement water has 10ppm. Then between water the water changes the tank must lower nitrates by 5ppm for it to have 5 ppm before the next water change.

Again just to give one a "feel" for what is happening.

my .02


----------



## whitetiger61 (Aug 2, 2011)

beaslbob said:


> But your analysis seems to be the transitory effects. The equation reflects the effects of regular maintenance and where the tank conditions finally wind up. With given tank conditions and water changes, the value before the water change is always the same.
> 
> For a 1/3 water change you mentioned:
> 
> ...


Ok here goes..if i get banned i get banned..Who cares about your equations..you are making this way harder on new people that it needs to be. new people come on here and see this stuff and think i dont want no part of that..i would if i were new..me i just shrugg off your non sense but now its going to effect new people, and this needs to stop. New people..do your water changes, for people with plants keep your nitrates up to keep plants healthy and call it friggin good..that's all i have to say

my .01

Rick


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> But your analysis seems to be the transitory effects. The equation reflects the effects of regular maintenance and where the tank conditions finally wind up. With given tank conditions and water changes, the value before the water change is always the same.


You're right, it is transitory or not always the same. There is no need to have it the same, but just ballpark. If I wanted to keep my planted tanks in the 20-40ppm range and it has reached 40ppm by the end of the week, a 50% change will get me to approx. 20ppm. By the end of the week I rise to 40ppm again and do the "normal" 50% water change gets me back to 20ppm. It does not continue to climb and climb if I control it and afterall, I do have the plants using up the nitrates as well. Also, I always advise people to test before their water change to determine the amount of change needed to get to a certain value. Your belief is that 0 nitrates is optimum, but that is largely unnecessary even for Discus, but much less so for most other species of fish....and I would even go as far to say "untrue" for a planted tank.

Like I said on water with nitrates in it...it is a rare occurance and there are other ways to take it down before you enter into the tank. So that discussion should be considered for the abnormal condition which exist in limited situations and refer to the normal conditions that mostly exist and talk just on that.


----------



## beaslbob (May 29, 2009)

jccaclimber said:


> More relevant comment. What are you trying to prove (1) and (2) Why are you picking such large nitrate values? Also, following this model the nitrates will rise to infinity without water changes. I doubt that's what you're trying to prove.


I have routinely seen posts from newbies where the question goes something 

I can't understand why i have nitrates (20, 40 ,80, 160ppm). I have been doing water changes and nitrates are high.


This equation should help people understand why nitrates are high (or just present) even though you have done water changes.


----------



## beaslbob (May 29, 2009)

whitetiger61 said:


> Ok here goes..if i get banned i get banned..Who cares about your equations..you are making this way harder on new people that it needs to be. new people come on here and see this stuff and think i dont want no part of that..i would if i were new..me i just shrugg off your non sense but now its going to effect new people, and this needs to stop. New people..do your water changes, for people with plants keep your nitrates up to keep plants healthy and call it friggin good..that's all i have to say
> 
> my .01
> 
> Rick


thanks for your feedback. And sure equations are confusing.

So what in you opinion should we tell newbies to do.

1) water changes (and at what level)

or

2) increase the nitrate consumers?

the boring equation should help determining which advice is best.


my .02


----------



## whitetiger61 (Aug 2, 2011)

beaslbob said:


> thanks for your feedback. And sure equations are confusing.
> 
> So what in you opinion should we tell newbies to do.
> 
> ...


dont throw equations at them..let them test their water like they are supposed to be doing, do water changes. all you are doing is confusing them..let them judge for themselves..dont go throwing mumbo jumbo at them because they dont understand it..

Rick


----------



## beaslbob (May 29, 2009)

whitetiger61 said:


> dont throw equations at them..let them test their water like they are supposed to be all you are doing is confusing them..let them judge for themselves..dont go throwing mumbo jumbo at them because they dont understand it..
> 
> Rick




Ok

so how about the question

I have high nitrates and have been doing water changes. Why?

Ans:

Water changes alone at normal levels will not result in low nitrates.

does that sound reasonable?


----------



## susankat (Nov 15, 2008)

beaslbob said:


> I have routinely seen posts from newbies where the question goes something
> 
> I can't understand why i have nitrates (20, 40 ,80, 160ppm). I have been doing water changes and nitrates are high.
> 
> ...



And if it gets down to it, they are doing very little water changes and not enough to make a difference and most are over feeding. The equation might work if you also showed the ratios of larger water changes where it does show a drop. All your doing is pushing no water changes by saying the nitrates rise with them, so that is not in a true sense good advice.


----------



## whitetiger61 (Aug 2, 2011)

beaslbob said:


> Ok
> 
> so how about the question
> 
> ...


wrong answer
correct answer..your overfeeding and not doing a large enough water change..im not saying new water doesnt have nitrates in it..im saying dont go throwing mumbo jumbo at people that dont understand you are just wasting valuable typing space

again my

.01

Rick


----------



## beaslbob (May 29, 2009)

whitetiger61 said:


> wrong answer
> correct answer..your overfeeding and not doing a large enough water change..im not saying new water doesnt have nitrates in it..im saying dont go throwing mumbo jumbo at people that dont understand you are just wasting valuable typing space
> 
> again my
> ...


Ok the poster says he's feeding a pinch every two days doing 10% weekly water changes and still has 100ppm nitrates.

What level of water changes does he have to do to bring nitrates down to 10ppm?

Oh no there's that boring equation again. LOL


(ans the weekly increase is 10ppm. they would have to do 100% weekly water changes)


How about the answer to increase the nitrate consumers? like with marine algae or Fw plants. Additionally, the current nitrate level could also be because the plant life in there is consuming ammonia not nitrates. In that case the extra plant life is safer as eventually the nitrates will come down as aerobic bacteria build up even if nothing is done.So nochange to the existing water change schedule or feeding is necessary.



my .02


----------



## susankat (Nov 15, 2008)

If that person would change 30% to 50% weekly that nitrate level will drop. Whether its a 1/3 or 1/2 it will drop that amount each time. 10% isn't a water change but more of a top off in my eyes.


----------



## whitetiger61 (Aug 2, 2011)

no you said you had high nitrates and were doing water changes as an example you didnt say anything about the poster..dont try mixing apples and oranges here.. all in all its wrong..everyone knows its wrong thats why you have crappy tanks

my .01

Rick


----------



## whitetiger61 (Aug 2, 2011)

susankat said:


> If that person would change 30% to 50% weekly that nitrate level will drop. Whether its a 1/3 or 1/2 it will drop that amount each time. 10% isn't a water change but more of a top off in my eyes.


and i totally agree with that..

Rick


----------



## beaslbob (May 29, 2009)

susankat said:


> ..
> 
> The equation might work if you also showed the ratios of larger water changes where it does show a drop.
> 
> ...


Within the assumptions presented (baciaslly everything is constant Including the change between water changes and enough water changes have been done so the value before a water change is always the same):

the equation not only works but accurately predicts tank conditions.

If anyone cares I can generate an excell (or open office) spread sheet showing this. Starting at day one until the final condition of the equation is reached. Just pm me or email [email protected]

(or you can generate your own it's not that hard. *old dude)

My .02


----------



## whitetiger61 (Aug 2, 2011)

just to confuse them more..i dont think so. like i said do their water changes and increase the volume of the water change and nitrates will go down.

Rick


----------



## susankat (Nov 15, 2008)

If you change more water conditions will not remain the same. For one they won't get as high and then another change will bring that amount down. 

I don't agree with the pinch of food. I can give a pinch and it could be too much food for an overstocked cichlid tank.


----------



## Reefing Madness (Aug 12, 2011)

The fish eat at will in the wild, i'm not a fan of calibrating what the fish eat. If the Trates are that high, you bring them down by doing 3-4 massive water changes. Ones at the 50-75% rate, every 2 days. I gaurentee this brings down those numbers rapidly. And if they go back up, it does no thave anything to do with the feeding, but all the stuff thats trapped in the substrate thats causing the issue then.


----------



## Reefing Madness (Aug 12, 2011)

jccaclimber said:


> Fish may eat at will in the wild, but food is less available and the dilution factor of nature is much higher.


True, but I've got HUGE fish, and I do not keep food from them. Do your water changes keep the trates in line, feed the fish. All is well. Or have one HUGE sump under your tank filtering the crap outta your water for you.


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> So what in you opinion should we tell newbies to do.
> 
> 1) water changes (and at what level)
> 
> ...


The answer is both for most of us...mostly you saying only one thing should be done. 

The answer is to control the nitrates and deal with it as necessary. Your way is unhealthy to plants and potentially unhealthy to fish. Your claims of how long your fish lived make it sound that way also, as most of the fish you've kept live longer than what you had them for.


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> I have routinely seen posts from newbies where the question goes something
> 
> I can't understand why i have nitrates (20, 40 ,80, 160ppm). I have been doing water changes and nitrates are high.
> 
> ...


Find me one newbie who has posted that they do regular 25% or higher water changes and still have that high of nitrates. Just one. I don't recall any like that.

And for your info, nitrates of 40ppm or below is fine and considered fairly normal....so exclude those. Only you have the idea in your head that a 0ppm reading is necessary.


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> Ok the poster says he's feeding a pinch every two days doing 10% weekly water changes and still has 100ppm nitrates.
> 
> What level of water changes does he have to do to bring nitrates down to 10ppm?
> 
> ...


LOL, not many out there doing 10% water changes and actually calling it that. You crack me up, dude! This is why the normal recommendation on here is at least 25% by most and as high as 50% by some of us.


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> Within the assumptions presented (baciaslly everything is constant Including the change between water changes and enough water changes have been done so the value before a water change is always the same):
> 
> the equation not only works but accurately predicts tank conditions.
> 
> ...


You can only give accurate info on your own tank. With anyone else's and trying to come to how they may have arrived at their current nitrate level, assumes that their habits are the same as yours, the bio-load is the same, etc.

Your equation does not work. Your assumptions are absolutely rediculous. It is entirely possible to do zero water changes on a heavily planted tank with a high bio-load and still have 100ppm nitrates...isn't it? Or did I just make some assumptions? A given Nitrate level is user induced, not some magical number derived at the fault of doing water changes....this is why your theory makes no sense. No matter how you do it, I bet that I can get a tank to near zero ppm of nitrates faster by doing water changes over not doing them....all with the same plants, same size tank, same bio-load, and both tanks not getting fed. Is that not true? Assumption is the water going in is good.....like 98% of us.


----------



## beaslbob (May 29, 2009)

jrman83 said:


> Find me one newbie who has posted that they do regular 25% or higher water changes and still have that high of nitrates. Just one. I don't recall any like that.
> 
> And for your info, nitrates of 40ppm or below is fine and considered fairly normal....so exclude those. Only you have the idea in your head that a 0ppm reading is necessary.





http://www.aquariumforum.com/f67/nitrates-high-cloudy-28473.html said:


> 30 gal reef and fish tank. The nitrate level has been high (danger level) The first thing I did was take out 5 gal. and replace it. That did not help





http://www.aquariumforum.com/f66/nitrites-nitrates-high-another-thread-26701.html said:


> and so have the nitrates (just as I would expect). However in spite of my frequent water changes up to 40%, I cannot lower the values.





http://www.aquariumforum.com/f5/nitrates-off-charts-23568.html said:


> The nitrate levels in my tank are maxing out my test kit every time.
> The water I use when I do water changes have very low levels of nitrate.
> I try to do 20% water changes every week or every other but nitrates still rise.





http://www.aquariumforum.com/f40/red-cherry-shrimp-nitrates-feeding-question-17412.html said:


> however when I tested today my nitrates are a little high. I did a 30% water change so hoping that helps.


While these may not be up to your level of concern I hope these few examples illustrate my point.


----------



## beaslbob (May 29, 2009)

jrman83 said:


> ..
> 
> Your equation does not work. Your assumptions are absolutely rediculous.
> 
> ...


Oh how so?

Sure things are constantly changing but assuming a constant rate of change and that the process has continued long enough to reach "end vaules" allows us to analyze how effective water changes are both in the short run and long run.

So you not believe the equations or the anwser?

Do you not believe that a 10% water change will eventually result in 10 time the changes between water changes? 20% 5 times? 33% 3 times?

Do you also not believe we can manage the system to reduce the rate of change to very low values?

the reef guys already know that and that is why calcium/carbonate/magnesium has to be added to the system even with very high levels of water changes.

my .02


----------



## susankat (Nov 15, 2008)

> Originally Posted by http://www.aquariumforum.com/f67/nitrates-high-cloudy-28473.html
> 30 gal reef and fish tank. The nitrate level has been high (danger level) The first thing I did was take out 5 gal. and replace it. That did not help


By my calculations thats not 25% and if that high is probably running a filter filled with stuff that grows nitrates. And is adding other gunk that probably isn't needed.



> Originally Posted by http://www.aquariumforum.com/f66/nitrites-nitrates-high-another-thread-26701.html
> and so have the nitrates (just as I would expect). However in spite of my frequent water changes up to 40%, I cannot lower the values.


I would almost bet there is an underlying problem of not pulling out dead plant matter or siphoning the bottom. And the tank isn't finished cyling. Needs to do water changes to keep the fish alive by removing nitrites. Not really anything to do with your equation.



> Originally Posted by http://www.aquariumforum.com/f5/nitrates-off-charts-23568.html
> The nitrate levels in my tank are maxing out my test kit every time.
> The water I use when I do water changes have very low levels of nitrate.
> I try to do 20% water changes every week or every other but nitrates still rise.


This person isn't doing large enough water changes and isnt doing them regularly.



> Originally Posted by http://www.aquariumforum.com/f40/red-cherry-shrimp-nitrates-feeding-question-17412.html
> however when I tested today my nitrates are a little high. I did a 30% water change so hoping that helps.


This one isn't even saying the nitrates remained high. Plus the fact that his plants are dying which will cause nitrates to rise, not the water changes.


----------



## jrman83 (Jul 9, 2010)

beaslbob said:


> Oh how so?
> 
> Sure things are constantly changing but assuming a constant rate of change and that the process has continued long enough to reach "end vaules" allows us to analyze how effective water changes are both in the short run and long run.
> 
> ...


None of it makes sense.

Do you agree that if I have a 100ppm nitrate tank that gets a 50% water change is reduced to 50ppm? That after a week if I managed to keep it no higher than 70ppm that the next 50% water change will get me to approx 30-40ppm? That if I manage to keep the nitrate to a 20ppm rise again (and this becomes my norm at this point) and do another 50% (also my norm now) that it gets me somewhere in the 20-30ppm nitrate level now? And if I continue to keep it there with discipline, that water changes help me stay >40ppm? This can be done without plants even...done it.

I would certainly agree that if you start with 100ppm nitrates and you don't have the sense to do larger than 10% water changes, you will be back over 100ppm by time the next regular weekly water change of 10% is scheduled. Your equations make perfect sense then. So if your whole point is if you do water changes, larger ones are better, I WOULD AGREE WITH YOU!! 

Do your equation with 50% and don't assume (what you have been doing all along) that the aquarist will not drive it back to 100ppm after 1 week has passed. If it doesn't get back to 100ppm, and 50ppm can be hard to hit in 1 weeks time unless it is being dosed in the form of KNO3, the aggregate total has to go down over time with regular 50% water changes. 

But, by all means plug in your numbers.


----------



## beaslbob (May 29, 2009)

jrman83 said:


> None of it makes sense.


I know because it took me years to come up with that equation.


> Do you agree that if I have a 100ppm nitrate tank that gets a 50% water change is reduced to 50ppm?


with 0 nitrates in the replacement water yes


> That after a week if I managed to keep it no higher than 70ppm that the next 50% water change will get me to approx 30-40ppm?


with 0 nitrates in the replacement water yes


> That if I manage to keep the nitrate to a 20ppm rise again (and this becomes my norm at this point) and do another 50% (also my norm now) that it gets me somewhere in the 20-30ppm nitrate level now?


with 0 nitrates in the replacement water yes


> And if I continue to keep it there with discipline, that water changes help me stay >40ppm? This can be done without plants even...done it.


 yes.

But please keep in mind the equation represents where the tank winds up at. for instance if you are doing a 50% water change with 0 nitrate water and the nitrates before the water change are 40ppm, the equation is simply telling you your tank is increasing nitrates at 20ppm between water changes.

Sure you can maintain 40ppm nitrates through water changes alone. Or any other value. if the tank is increasing at 40ppm then do a 100% water change. 20 ppm 50 %, 10 ppm 1/4, 5 ppm 1/8, 1 ppm 1/40 etc etc. assuming 0 nitrate water.



> I would certainly agree that if you start with 100ppm nitrates and you don't have the sense to do larger than 10% water changes, you will be back over 100ppm by time the next regular weekly water change of 10% is scheduled. Your equations make perfect sense then. So if your whole point is if you do water changes, larger ones are better, I WOULD AGREE WITH YOU!!


larger water changes also result in the greatest tank variations. More frequent smaller changes can result in the same values before each water change with less change after the water change.


> Do your equation with 50% and don't assume (what you have been doing all along) that the aquarist will not drive it back to 100ppm after 1 week has passed. If it doesn't get back to 100ppm, and 50ppm can be hard to hit in 1 weeks time unless it is being dosed in the form of KNO3, the aggregate total has to go down over time with regular 50% water changes.
> 
> But, by all means plug in your numbers.


Again the equation applies to where the end point is. for instance if you have 100ppm before the water change with a 50% water change that means the tank in increasing nitrates at 50ppm between water changes. Up to 100 down to 50 up to 100 again. And as usual assuming 0 nitrates in the replacement water.


----------



## jrman83 (Jul 9, 2010)

Okay, sounds like we sort of agree then. Water changes if done correctly, can positively impact high nitrates.

I just never look at it as some equation. If I know that there is already some positive value nitrate level "after" my water change and anything that occurs between then and the next water change is only added to whatever that value was. Simple math to me. The key is larger water changes, especially those in the 10-20% range.


----------

