effectiveness of water changes

[Anonymous]

For the newbies reading this, one of the more conterversial aspects of "my" methods is not conducting water changes. The purpose of this thread is to simply evaulate exactly how effective a 10% weekly water change is. Therefore I will just focus on that aspect of the usual advice and practices. Regardless of what is in this thread everyone will probably continue doing or not doing water changes regardless.

It is my hope that every newbie who ever walked out of a LFS with $20-50 of salt thinking that water changes will maintain trace elements reads this thread.

To evaluate the effectiveness of water changes I will consider the effects of water changes and only water changes. This is obviously not what happens in our tanks but does show how effective water changes are.

Consider:

Period starting value=PS
Period change=PC
Water value=WV
Water change amount=amt. (fraction)

By using concentrations the actual volumn is not important. The same will be true for a 10g or 2000g system. Just that a 10% water change on the 2000g requires more water is all.

Period ending value=PS+PC (start+change)

After the water change we have:

(1-amt)*(period ending value)+amt(WV)
Or
(1-amt)*(PS+PC)+amt*(WV)

The net change after the water change is the value before the water change minus the value after the water change

Period ending value-[(1-amt)*(PS+PC)+amt*(WV)]

or

(PC+PC) - [(1-amt)*(PS+PC)+amt*(WV)]

The system will converge upon the situation where the change caused by the water change equals the change the system experienced between water changes. So:

PC=(PS+PC) - [(1-amt)*(PS+PC)+amt*(WV)]
Simplifying the PS+PC on the right
PC=-(-amt)*(PS+PC)-amt*(WV)

Solving for the period starting point PS:

PC=+amt*(PS+PC)-amt*(WV)
Amt*(PS+PC)=PC+amt(WV)
Amt*PS =PC-PC*amt+amt(wv)

PS = (1/amt - 1)*PC +WV


edit:

The parameter just before the water change is easier to remember:

just before water change (PS+PC)=WV+PC/amt

So for a 10% water change just before a water change the parameter becomes the water change value+10 times the period change.

end edit

So say you want 0 something but that something is building up at 10ppm between water changes. And the replacement water has 0 somethings . Say nitrates. With a 10% water change

PS= (1/.1 - 1)*10 + 0 = (10-1)*10 = 9*10= 90

Just to check 90 goes to 100 between water changes. A 10% water change with 0 ppm water results in 90 PPM for the start of the next period.

Now consider something being consumed at 5ppm with water change water at 425.

PS=(1/.1 -1)*-5+ 425= 9*-5+425= -45+425=380

380 drops to 375. .9*375=337.5 + .1*425=42.5 337.5+42.5=380


If 1350 is in the replacement water and the system decreases at 20 between changes

Then 1170 goes to 1150

If it increases at 20 then 1530 to 1550

The point is that water changes even assuming correct replacement water will never maintain any parameter know or unknown at that value.

In order to maintain stable more constant and optimal values the system must take care of those things itself or you must replace things that are being used up. Therefore, you dose such things as calcium. What I do is basically allow things to be present which are being brought into line with plant life. But what ever you do just don't be surprised when things build up, can't be maintained, or otherwise go south, when doing water changes. Partial water changes will never correct adverse trends.

 

[HClH2OFish]

Wow!!!

Bob went and bought a science book!!!

Simply put for all you 'newbies' who are reading this -- please do a search on other threads and you'll find that Bob's methods are definitely not ones advocated by *any* successful reefer with any experience under their belt. Even though he's got tons of posts and his tag shows he's got years and years of experience, he doesn't have reef experience. Sorry Bob -- what you have I seriously don't consider a reef. Maybe a lagoon environment from the looks of the tank, but definitely not a reef.

About the only thing I'll agree with him on is that it's a great idea to have a sump/fuge -- but not a necessary one as he claims.

Oh, as for the scientific mumbo jumbo -- it's simply clouding the issue, and an attempt to get a few lines from some post that he can quote in an attempt to try and show that he has the support of someone who disagrees --

You take out garbage - you have less garbage.
That's why larger tanks tend to be more stable "Dilution is the solution for pollution" to quote a great reefer that I can't remember right now :lol:

 

[Anonymous]

Partial water changes will never correct adverse trends.

LOL Bob, your methods are the most likely "adverse trends".

Water changes do not fix everything. There is nothing that fixes everything. Water changes help. As do skimmers, RO/DI water, heaters, live rock, etc. All the things you advocate against help in a small way. Combined they create a healthy reef environment.

 

[Anonymous]

wow, so my tank is simply a math equation? Well sh*t I can do that..

 

[Anonymous]

I advocate regular water changes.

 

[Anonymous]

(said in a deep, DEEP voice -- so deep it can barely be heard)




As usual, I agree with Chrispy!




(end of deep, DEEP voice -- so deep it can barely be heard)

 

[npaden]

For anyone that actually wants to read and understand the affect of waterchanges on your tank you might try to read a comprehensive article written by someone who doesn't have an agenda and writes in a much more readable fashion and even has graphs!

Here's the link:

http://www.reefs.org/library/article/t_ ... ll_wc.html

FWIW, Nathan

 

[ZooKeeper1]

So what do you think if you confuse people they will believe you? That is some of the worst advice I have ever heard. Not everybodys tank builds things as fast as water changes dilute them.You make too many assumptions, and obviously dont understand simple husbandry. Obviously in a tank like yours where nutrients abound small water changes wouldn't help much, but large ones would, try it you might be surprised with the results. It still comes down to a balanced import and export of nutrients

 

[Oceans Ferevh]

Salt is expensive, but I notice a large positive effect whenever I do a water change. Thus, because of my personal experience with these benifits, plus overwhelming volumes of data that supports these effects I will continue to do water changes.

 

[reefmongrel]

Agree totally with everyone re water changes. For those who don't think water changes are important, seal up your house and breathe the same air for a month - then do the math/chemistry on that - if you have enough o2 left that is......

 

[Anonymous]

For the newbies reading this, one of the more conterversial aspects of "my" methods is not conducting water changes. The purpose of this thread is to simply evaulate exactly how effective a 10% weekly water change is. Therefore I will just focus on that aspect ofthe usual advice and practices. Regardless of what is in this thread everyone will probably continue doing or not doing water changes regardless.

Before bothering with the rest of your post, who recommends 10% weekly water changes?

 

[Mihai]

This post would be almost funny if I would not know PLB.

Who ever claimed that you can reduce bad things to zero by water changes? Perhaps more importanly - who said that you have to? Things have just be be eliminated to some point. Even in the nature they are not zero (nothing is zero!). If you don't eliminate things they accumulate and your tank looks like this:

 

[bradl.]

This post really makes me wonder. Not about the ridiculous subject but Bobs motives. Is this an attempt at educating new hobbiests or to confuse them.I dont know what the formulas he posted are and Im sure he doesnt either. But I can tell you this.I used to feel bad for the way ppl treated him and his ideas about reef keeping.But I think he enjoys the attention.

 

[Anonymous]

This post really makes me wonder. Not about the ridiculous subject but Bobs motives. Is this an attempt at educating new hobbiests or to confuse them.I dont know what the formulas he posted are and Im sure he doesnt either. But I can tell you this.I used to feel bad for the way ppl treated him and his ideas about reef keeping.But I think he enjoys the attention.

I think you are right about the attention.
Bob has been told this 'work' on waterchanges has already been done and understood, he has even been given the link to the Troy Brightbill article, so I don't really understand the point of the post.

 

[HClH2OFish]

This post really makes me wonder. Not about the ridiculous subject but Bobs motives. Is this an attempt at educating new hobbiests or to confuse them.I dont know what the formulas he posted are and Im sure he doesnt either. But I can tell you this.I used to feel bad for the way ppl treated him and his ideas about reef keeping.But I think he enjoys the attention.

Exactly...after following his posts on this board, I'm still leaning more towards the 'troll' label than anything else. It seems he puts most of this info up to see who he can get to jump. And trying to be responsible and protect new reefers from going down a poor path, we have no choice.

His posts are either 1) Amusing or 2) Maddening, but rarely 3) Informative

 

[Anonymous]

My response to bob's latest trolling effort are water changes worth it? As my dear ol' Daddy used to say...


The solution to pollution is dilution.

 

[leftovers]

My response to bob's latest trolling effort are water changes worth it? As my dear ol' Daddy used to say...


The solution to pollution is dilution.

which explains why we have the problems we do in the world.

The solution to polution is to not create it in the first place.

For "natural polution" i.e. waste created by captive kept pet. Dilution is only one small part of the problem. Where does that polution come from? How much am I, the external, adding to it with food and other additives?

Eliminate/reduce the source and dilution becomes irrelevant as the system becomes more fault tolorant.

I'm not advocating 0 water changes quite the contrary.

I only advocate eliminating any water change that's less than 30%. I only do water changes that are 40% or more and really would like to see people do 50% changes every few months. To bad i know that this will never happen; the excuses will now begin, too hard, no place to keep water, no money blah blah blah blah...

 

[Anonymous]

I would be really nervous changing 500 gallons of water. I would think that could be an irritant or even a shock if it hadn't been changed in a few months. But, I have an open mind. Why do you feel that 50% every few months is better than 20% a month?

 

[Anonymous]

I only advocate eliminating any water change that's less than 30%. I only do water changes that are 40% or more and really would like to see people do 50% changes every few months. To bad i know that this will never happen; the excuses will now begin, too hard, no place to keep water, no money blah blah blah blah...

Why?

 

[RobertoVespucci]

My response to bob's latest trolling effort are water changes worth it? As my dear ol' Daddy used to say...


The solution to pollution is dilution.

If that were true all of you ganging up on bob would make him go away.



In my very biased and occasionally honest opinion, coming from my very n00b perspective, that you all give a rat's ass what bob thinks/says is just egging him on and encouraging him.

I'm hoping that atleast one of you is more concerned over him giving n00bs like me bad advice than you are about being 'more right' than bob. To you I say: Thank you! And every time bob speaks of despicable practices, just post the following:

Our way!

Bob's way!