Adding Fuel to the Nitrate Debate: Why Water Changes DONT Reduce Nitrates

[cichlid savage]

I think that you cant use and arbitrary definition like units and compare it to percentages. Once you do the water change the percentage of nitrates in the water goes down according to the volume changed. so if you change 50% of your water and that removes 30% of your nitrates then after you add 50% clean (nitrate free) water your nitrates are now 15%. I think. I am by means no expert but that is my understanding. Help me if I'm wrong.

 

[Lil_Stinker]

Okay kids..

Lets look at the math.....

After 20 weeks of 50% WC there will be a stable 20 "portions" of waste
Take 1/2 the water out you are down to 10 "portions" of waste
1 week later you are at 20 "portions" of waste
Take 1/2 the water out you are down to 10 "portions" of waste
1 week later you are at 20 "portions" of waste
Take 1/2 the water out you are down to 10 "portions" of waste
1 week later you are at 20 "portions" of waste
Take 1/2 the water out you are down to 10 "portions" of waste
1 week later you are at 20 "portions" of waste
Take 1/2 the water out you are down to 10 "portions" of waste
1 week later you are at 20 "portions" of waste

see a patern here?
looks stable to me.

or wait 2 weeks to do WC#1 & then your tank is balanced between 10 & 20

see the modified example

We start our calculation assuming we had zero nitrates initially..

Week 1
nitrates produced in one week = 10units
Total nitrates in aquarium = 10units
No water change
Week 2
initial nitrates in aquarium = 10 units
nitrates produced in one week = 10 units
Total nitrates in aquarium = 20 units
End of Week 2, 50% water change, resultant nitrates = 10 units
Week 3
initial nitrates in aquarium = 10 units (from the day before)
nitrates produced in one week = 10 units
Total nitrates in aquarium = 20 units
End of Week 3, 50% water change, resultant nitrates = 10 units

Week 4 to forever
initial nitrates in aquarium = 10 units (from the day before)
nitrates produced in one week = 10 units
Total nitrates in aquarium = 20 units
End of Week, 50% water change, resultant nitrates = 10 units

As you can see; a WC WILL reduce everthing the the water

"The solution to Pollution is Dilution"

 

[shekes]

And if you dont have a bottle of milk, you can always use coke instead.

 

[repair]

Shekes you know I don't use my being a moderator as a weapon.....

OK think of it this way.

If the fish could get the tank to 100% nitrates you would still lower the tank to 50% nitrates at the water change.

Keep in mind that we are not talking about % of volume when we talk about nitrates, we are talking about so many parts per thousand.

So if the fish could raise the PPT by 50 PPT each week we are going to lower the number by more than 50% each water change.

 

[koliveira]

This is a quote from article!Lastly, this article does not condem water change. Water change is very much an essential part of fishkeeping as it renews the water coming into your aquarium system. Water change is also an important emergency action when your water is contaminated or has high levels of waste (even nitrates). What this article tries to show is how water change is not a long term solution to the problem. If your aquarium has no facilities that controls nitrates, sure, continue your water changes to "control" nitrate as keeping your nitrates at a high level is better than letting it rocket from high to higher.


This really does not make sense! I have had a 40g for 6 years in the same location Same gravel in the tank same fake plants no live plants and I do a 40% water change every two weeks. My nitrate levels are never above 40ppm...b acording to this article all my fish should be dead and my nitrates out of control!!

This whole article is flawed and should be discarded!

 

[Guinness]

Your thinking is flawed.

"The waste in the tank on the evening (after a WC) of the first day = W(1-WC%)

Waste in the tank after second day (after WC) = W(1-WC%) + W(1-WC%)(1-WC%)

Waste on third evening = W(1-WC%) + W(1-WC%)(1-WC%) + W(1-WC%)(1-WC%)(1-WC%)"



Your equasions are incorrect, don't believe everything you read on the internet. These equasions do not reduce the prior days waste by any percent only the daily added waste. I played with the idea a little and this is what I came up with.

Day 1 Day 2 Day 3
W(WC%) + (W(WC%)+W)WC% + ((W(WC%)+W)WC%)+W)WC% and so forth.


The limit to this equasion depents on your value for W and WC%. For example, if you use 10 for W or the number of waste units and assume 50% water changes, the limit prior to any water change is 20 units of waste and 10 units of waste after a water change.

So if you have a 100 gallon tank and it's inhabitants add 10 ppt nitrate per day, and you to a 50% water change every day, your nitrates will never reach 20, but they'll get really close.

 

[DeLgAdO]

im already set

i do 2 75% water change twice a week

 

[shekes]

Shekes you know I don't use my being a moderator as a weapon.....

Had I thought that you I wouldn't be answering you. Unfortunately I can't concentrate on that right now and apparently Guiness discovered a mistake in the formula I copied it from the discus-site. So I have to review that and your post (before I answer some bullsiht) and come back.

Your equasions are incorrect

They aren't mine but I did make the mistake of posting them without reviewing. I will produce a correct formula later on myself. It isn't rocket science though, as the example with a bottle of milk should illustrate.

 

[Burtess]

So if you have a 100 gallon tank and it's inhabitants add 10 ppt nitrate per day, and you to a 50% water change every day, your nitrates will never reach 20, but they'll get really close.

Guinness has the correct logic.

And if you do the calcs as in JardiniBoy's initial post, but continue to week 5, 6, etc. it will creep very close to but not equal to 20.....

The article is like one of those strangely worded jokes that lead you to believe something that isn't true......

Burt

 

[Primus]

Lets see if we can find a way to test the long term effect of water changes on nitrate levels in an aquarium that has no live plants etc to process nitrates. Hmmmm...........

Does anyone here do weekly water changes? Does anyone test for nitrates every time they do water changes? I for one can answer yes to both of those questions and from experience can say that it is very easy to control nitrate levels with only water changes. I think there are many fish keepers who frequent this site that can also say yes to both those questions.