Mathematical approach to waterchanges

[pascal]

Just some words of explanation to illustrate :

Dynamic equilibrium : consider it is winter and you want to shelter in a cabine in the woods. To warm you up, you can make a fire inside with wood. The cabine is rudimentary and not thermally isolated. Inside it will be warmer after a while, but there wil be losses of heat. As the temperature increases, the losses in heat will be higher because the difference in temperature inside and outside is higher. At a moment, the heat coming from the fire will be equal to the loss of heat. From that moment on, temperature will remain constant.

If I add a piece of wood that is extra dry, temperature will be higher for a moment. If I add a wet piece of wood, temperature will decrease for a short moment. That is true. An estimation is consider the mean quantity of heat that is produced by the wood I'm burning.

So, consider no feces is removed. It is just decomposed into nitrate. In this case it is assumed that it is a steady state situation : constant addition of a constant quantity of feces, resulting in a constant "addition" of nitrates in the tank. This is a simplification, a first approach.

If there is an accumulation of waste in the filter, nitrate concentration can be higher for a moment, but that means that less waste was eliminated formerly. But over a longer period, waste accumulated in the tank can never be higher than the amount added, where should it come from? (In physics, this is called the principle of continuity). So as a mean, what is added is equal to what is eliminated if we are at equilibrium.

[pascal]

You are answering faster than I can reply.

Do not think this approach is against daily waterchanges. I perform as a mean 100-120% on a weekly basis (15% daily), which is much less than you apply. But I have 6 angels in a 350l tank and I have them 6 years now (they are wild caught and were adults when I bought them). On the other hand, even if the formula indicates that only 50% WC weekly is needed to get at the desired nitrate concentration, it does not mean that more frequent WC are not useful. I'm in favor of daily waterchanges. If I could, I would change more. So I'm totally in line with that statement.

On the other hand, facts and opinions from people with experience are most valuable and I have the highest consideration for that.

[rickztahone]

Just some words of explanation to illustrate :

Dynamic equilibrium : consider it is winter and you want to shelter in a cabine in the woods. To warm you up, you can make a fire inside with wood. The cabine is rudimentary and not thermally isolated. Inside it will be warmer after a while, but there wil be losses of heat. As the temperature increases, the losses in heat will be higher because the difference in temperature inside and outside is higher. At a moment, the heat coming from the fire will be equal to the loss of heat. From that moment on, temperature will remain constant.

If I add a piece of wood that is extra dry, temperature will be higher for a moment. If I add a wet piece of wood, temperature will decrease for a short moment. That is true. An estimation is consider the mean quantity of heat that is produced by the wood I'm burning.

So, consider no feces is removed. It is just decomposed into nitrate. In this case it is assumed that it is a steady state situation : constant addition of a constant quantity of feces, resulting in a constant "addition" of nitrates in the tank. This is a simplification, a first approach.

If there is an accumulation of waste in the filter, nitrate concentration can be higher for a moment, but that means that less waste was eliminated formerly. But over a longer period, waste accumulated in the tank can never be higher than the amount added, where should it come from? (In physics, this is called the principle of continuity). So as a mean, what is added is equal to what is eliminated if we are at equilibrium.

According to this logic, how long would feces take to fully break down? At what point do you pass the 10/20/30ppm threshold? Do you eliminate the nitrates by that time before the accumalation "eventually" decomposes in to nitrates?

[John_Nicholson]

Plain and simple here i what you do. Setup 2 tanks and buy 12 small discus. Make one bare bottom. put in 6 small discus, feed them well, and change at least 50% of the water a day. The second tank set it up anyway you want. Put in 6 small discus and feed them well. Do whatever yuu want that you think will work. In 12 months post your results. I don't mean to sound like a *** but nothing that you are throwing out here is even remotely new. Several times a year some new person will come in here and start making the same "thoughtful and scientific" thoughts. Most will claim success for about 4 months and them they disappear because they realize they were wrong and they do not want to admit it. I support your right to treat your fish however you want to I just don't want you to mislead any other new discus hobbyist. Also you can pretty much raise angels in a cess pool. They water requirements are not even close to those of discus.

-john

[rickztahone]

You are answering faster than I can reply.

Do not think this approach is against daily waterchanges. I perform as a mean 100-120% on a weekly basis (15% daily), which is much less than you apply. But I have 6 angels in a 350l tank and I have them 6 years now (they are wild caught and were adults when I bought them). On the other hand, even if the formula indicates that only 50% WC weekly is needed to get at the desired nitrate concentration, it does not mean that more frequent WC are not useful. I'm in favor of daily waterchanges. If I could, I would change more. So I'm totally in line with that statement.

On the other hand, facts and opinions from people with experience are most valuable and I have the highest consideration for that.

Consider the fact that if you do 15% WC's daily, it isn't additive as you proclaim. By the end of the week, although you may think you have additively removed 105% (15% daily WC's), in fact, you have not.

[rickztahone]

Just to add, me asking these questions is not to try to get under you skin. I am simply not seeing what you are seeing and would like to have a thoughtful conversation about it.

[nc0gnet0]

A couple of issues with your calculations. Your making the assumption that the nitrates are evenly distributed throughout the water column. What Rick was alluding to is that wastes can accumulate in places such as filters, under substrate, etc etc that make this assumption false, ergo a 15% change in water will not result in a 15% reduction of nitrates and or nitrate producing material (uneaten food which is decomposing, fish feces, etc etc). Also, it does not allow for the synthesis of simple and complex proteins within the fish themselves, for instance, the discus slime coat.

[strawberryblonde]

I know that my views towards fish keeping are very simplistic but I did actually enjoy reading your calculations and had never really had a name such as dynamic equilibrium for the ratio of nitrates to water in my tank - so than k you for that.

For my own fish keeping, here is the simple method that I use in order to maximize the health of my fish through water quality.

I grab my nitrate test kit and test the water just prior to a water change. I note it and if it is higher than 5ppm, I increase my water changes - either the amount at each change or the frequency of changes.

I continue testing just prior to each water change until I've brought the nitrate levels below 5ppm. At that point I only test when there is a change to the conditions in my tank, ie: adding more fish, more decoration, changing substrate, etc.

The only other maxim that I adhere to is to commit to large (At least 80% and preferably 90%) water changes daily while growing out fish to their maximum potential.

[Rudustin]

I know that my views towards fish keeping are very simplistic but I did actually enjoy reading your calculations and had never really had a name such as dynamic equilibrium for the ratio of nitrates to water in my tank - so than k you for that.

For my own fish keeping, here is the simple method that I use in order to maximize the health of my fish through water quality.

I grab my nitrate test kit and test the water just prior to a water change. I note it and if it is higher than 5ppm, I increase my water changes - either the amount at each change or the frequency of changes.

I continue testing just prior to each water change until I've brought the nitrate levels below 5ppm. At that point I only test when there is a change to the conditions in my tank, ie: adding more fish, more decoration, changing substrate, etc.

The only other maxim that I adhere to is to commit to large (At least 80% and preferably 90%) water changes daily while growing out fish to their maximum potential.

I do exactly the same thing. Rufus

[afriend]

pascal,

farebox,

First, thanks for a really great presentation, nice job.

Would like you to comment on another aspect of nitrates. I have been using a SeaChem product called Purigen for about three years now, and have been getting really great results in reducing nitrate. Purigen is an absorbent. It does a really great job of reducing organic compounds in the water column (Purigen does not absorb ammonia, nitrite, or nitrate). As a result of reducing the organic compounds, the nitrate level in my tank is zero (ie bright yellow as measured by an API nitrate test kit). This is accomplished with 30% daily water exchanges.

The question I would like you to consider is this: Limiting the discussion to contaminants caused by foods, what other considerations are important other than the production of nitrate? In my case, since I have reduced nitrate to zero, what else is important?
Paul

[DonMD]

Setup 2 tanks and buy 12 small discus. Make one bare bottom. put in 6 small discus, feed them well, and change at least 50% of the water a day. The second tank set it up anyway you want. Put in 6 small discus and feed them well. Do whatever yuu want that you think will work. In 12 months post your results.
-john

This would be a simple scientific experiment to validate the theory, I believe. Why not give it a go? All theory, except I suppose in those in high mathematics, must eventually succumb to proof. Or as my grandma always said, the proof is in the pudding . . . LOL.

[MadMatt]

I love science and I appluad you thoguts but in reality iy just does not really work this way. Lots of people have rolled in here and tried these things. At the end of the day just change water and you will be miles ahead.

-john

Brother you have a way with simple but powerful words, I have to agree.

[MadMatt]

The fact of the matter is this, many variables are not yet proven and or discovered yet by science or comprehendible By human thinking. We as a human species would like to believe we have a good grasp of all proven concepts and proven theories. However as we as a human species age, we find out that many theories and concepts have been from marginal to drastically flawed. The ideal of the understanding of water is no where near close to being understood, this non-understanding variable makes most theories of aquatic care very difficult to put into successful practise.
But, do not get to discouraged. Moreover, the world needs people to attemp to understand, the world needs different ideas and to attempt different thinking, concepts and to attempt many different practises and put ideas into actions, this is how new discoveries are made. For nothing is really invented but merely the human understanding of how complex machanics of this earthly experience behaves and outcome of many different characteristics.
Moreover the world needs people like this to try many different and like,same ideas. To explore a once tried and failed concept but put a new perspective on it is honorable, but sometimes the same failure is the same outcome but with new information discovered, this would be argued it's not a failure at all.
I commend you for attempting something visited and now revisited for a succesful outcome. Threw trying is where new thing are discovered.
Best of luck and put it into practise and see what happens.

[pascal]

Thanks a lot to all for your comments and your interest.

[afriend]

I love science and I appluad you thoguts but in reality iy just does not really work this way. Lots of people have rolled in here and tried these things. At the end of the day just change water and you will be miles ahead.

-john

About a hundred years ago the general thought was "the horse drawn carriage works just fine, why would anyone want to invent something called an airplane?"

Just a friendly thought.