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

[mdb_talon]

but the problem with the math is that it assumes that the source of the nitrates remains constant.

it doesn't.

it is a flawed way of looking at the system.

when you do a water change, you are not only removing water that has a given concentration of nitrates, and then diluting what is left in the tank, you are also removing detritius/ammonia etc that would have been eventually broken down into nitrates later on...

thats why saltwater folks use protein skimmers for example - get the wastes out before nitrates have a chance to be formed in the first place...

the math does not take this into account..

LOL I said the conclusion was wrong..... The bigger problem with the conclusion though is he did not go far enough. If you extend his math out another few weeks even by his example equilibrium would be reached where every week 10 units are removed and 10 remain (approximately) which means with water changes Nitrate levels remain approximately stable over the long term rather than increasing constantly. It is the same exact math that people later in the thread use they just showing the same math after equilibrium has been reached. Thats why I say his math is correct just the conclusion wrong.

 

[wow_it_esploded]

Nirates will not kill your fish

(dpending on what species of fish it is) they have to be exposed to high concentrations for a long time (years) before you even notice any problems.

tho some are more senstive that others i.e (rays,discus).

nitrates will not kill your fish, however, dissolved organic compounds will.

thats what you should be more worried about.

nitrates are just a component of the total dissolved solids in your water.

I do not have time to read this entire thread, but nitrates will kill your fish. 200ppm of trates have been shown to be lethal.

 

[selki]

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"

i agreeeeeeeeee

 

[hailmike]

i hate math i prefer art

 

[hybridtheoryd16]

This is why any toxin is measured in parts per million. Because the 10 units of waste may be a big deal in a small amount of water and not a big deal in a larger volume. Also PPM helps to understand exactly what is going on in a aquarium. Before a Wc say you have 50ppm if you do a 50% water change and the water going back in the tank is say zero nitrate then the after WC reading for nitrate is alot lower than 25ppm. Because the incoming water dilutes the left over nitrate. And that is how you lower the nitrates with more larger water changes.

 

[duke33]

Howdy,

I think whoever posted the original also posted that his/her conclusion is wrong: By the end of week 4, he calculates 9.37 units. Without water changes, it would be 40 units. Now tell me how someone could possibly conclude that water changes do not reduce nitrates They're down to 1/4 !!!

The truth is, water changes cause pollutant levels to asymptotically reach acceptable steady state levels instead of continuing with linear increase.

HarleyK

 

[brianhellno]

I guess I'll contribute a handy little calculator.

http://www.theaquatools.com/water-changes-calculator

Just replace the word dirt with nitrate and it calculates a water change schedule and what would happen if you stuck to the water change schedule. This is all assuming of course that every day your tank will produce the same amount of "dirt" and that nothing will ever possibly go wrong.

 

[Jgray152]

Umm. Regardless of what size water change you do, you will reduce nitrates. Maybe the OP wanted to say that water changers do not eliminate nitrates??

 

[Zander_The_RBP]

water changes DO reduce nitrates and i know that this has already been said but im guna repeat it and prove something else while im at it

assuming were producing 10 units of nitrate a week and doing 50 % water changes we eventualy reach 20 nitrates / 2 = 10 plus another 10 units of nitrates aka the level is stable as long as your not off on your water changes it will remain stable

now lets say we do 75% water changes while the fish are still producing 10 units of nitrates eventualy the level stabilizes out at 3.33 units of nitrate 20 vs 3.33 thats a huge difference while were only changing 25% more

so everyone do larger water changes !

 

[tcarswell]

i HATE people who think that they can explain away all our problems on paper but in the reality of it all the practicality is so far off base that its all wrong. Happens all the time. Engineers tell the techs the way it should be, but the techs do it the way it works.

woah woah woah

Ok this strikes a cord as I am working as a HVAC-R technician and going to school for an engineering degree. Yes sometimes engineer's draw up things that are not feasible on a job site while in the planning process. Trouble being that usually the framers , or tech before you varied from the plans to make his job a little easier. This is very seldom the engineers fault. In my 8 straight years of working 5 days a week and the 6 years before that working 20 hours a week I have only come across two genuine engineers mistakes. However the person that wanted their home built had sent the plans to engineers who were never able to set foot on the job (They were in LA ) and the job was in Santa Lucia.
Also remember that a lot of people blame engineers to seem smart on the job when its usually an "architects" redesign that fails.



And to keep this thread on course..... I do 2 50% water changes a week on all my tanks with gravel vac. Nitrate from the tap is 20 (The reason for such changes) I was first under the impression my nitrate would be 20 NOPE
I test bi weekly one before the first water change once after the second. I usually run around 30-40 because there is a variable that I have not seen mentioned... How much I feed the fish if I overfeed that number crawls up but eventually it all levels around 5 ppm with the two changes. This is all done with a seachem nitrate /nitrite test kit.