Water Changes And The Build Up Of Nitrate Levels

[stu40]

So I read somewhere that in an optimum set up, plants only remove a max of 5ppm Nitrate (Tom Barr?).
If one of the reasons for water changes is to remove nitrates,what happens in tanks that go unchanged for long periods of time, why does the nitrate level not build up?
Is it because the plants process/use/absorb large amounts of ammonia & nitrite,therefore removing them from the Nitrogen cycle.The bacteria colony then process what's left into nitrates.Some of which is also used by plants.
In these setups is it just that the weekly,nitrate rise is so small that it takes months to get to really significant levels (100ppm say).I don't know how much nitrate would be produced weekly, but even at say 5ppm and a starting level of 10ppm in the tap water it would take 18 weeks to reach 100ppm.
So i guess the knack is to balance your bioload with your plant mass to minimise nitrate production and prolong the time periods between water changes?
I'm not looking to use this an excuse for less maintenance, just trying to understand the underlying principal.
Am i missing something obvious?

 

[StandbySetting]

There are many variables; to name a few:

You're correct about Tom Barr and the maximum uptake of 5PPM, this was with 45PPM of CO2 and 6WPG, in normal circumstances the uptake will be lower, but plants will utilise ammonia ahead of nitrate.

Anaerobic bacteria exist on plant roots and sometimes in pockets in the substrate, they can fix nitrate and convert is into ammonia, they respire by using nitrate as an electron acceptor in the place of oxygen during respiration

But usually on tanks that go without water changes for large periods, the plant mass is high and the stocking is lower than what you would call your average.

 

[Geoff-]

5ppm is a concentration, not a rate of anything.


the principle of reducing your nitrate levels is balancing plants and animal biomass, yes. it also depends heavily on how much you feed - basically any fish food you introduce will end up as ammonia or nitrates whether processed through a fish or left to rot. your minimum feeding level depends on how many fish you have. plants reduce ammonia and nitrate levels at a certain rate, and beneficial bacteria convert ammonia into nitrates at a certain rate (for a properly set up tank, this is usually fast enough that ammonia registers 0 on a test chart).

 

[stu40]

5ppm is a concentration, not a rate of anything.


the principle of reducing your nitrate levels is balancing plants and animal biomass, yes. it also depends heavily on how much you feed - basically any fish food you introduce will end up as ammonia or nitrates whether processed through a fish or left to rot. your minimum feeding level depends on how many fish you have. plants reduce ammonia and nitrate levels at a certain rate, and beneficial bacteria convert ammonia into nitrates at a certain rate (for a properly set up tank, this is usually fast enough that ammonia registers 0 on a test chart).

Ok, so, i should have put that the rate of production results in a concentration increase of 5ppm (5 is an arbitary value, i don't know what it is, in this tank set up).
By using the term "bioload" in the OP, i thought that included feeding levels as well as stock levels,decomposing plant matter.etc (i.e things that introduce ammonia).Hopefully it's the theory behind it, that i'm getting close to understanding.The terminology is something to work on.

 

[aaronnorth]

Have a read of this;

http/www.fishforums.net/index.php?/topic/204993-no3-dosing-toxicity-for-fishshrimp/

There are many variables; to name a few:

You're correct about Tom Barr and the maximum uptake of 5PPM, this was with 45PPM of CO2 and 6WPG, in normal circumstances the uptake will be lower, but plants will utilise ammonia ahead of nitrate.

5ppm over what time period?

Aaron

 

[StandbySetting]

Sorry I should of mentioned, over a period 1 day if memory serves me correctly.

 

[aaronnorth]

Sorry I should of mentioned, over a period 1 day if memory serves me correctly.

EI was calculated on a maximum uptake rate of 20ppm NO3 per week, so that wouldnt work out

Thanks, Aaron

 

[StandbySetting]

Was that with the 6WPG and 45PPM of CO2, I'll have a read through it on the Barr Report again to refresh my memory.

 

[aaronnorth]

Yes, I have just read the guide on here, it says 5pm x3 per week - perhaps this is where the confusion lies?

 

[StandbySetting]

It could be, it's been a while since I've read them both, I'll take a look, cheers

 

[aaronnorth]

Well anything below 20ppm is limiting. Anything above 30ppm won't give you much better growth rates.

Thanks, Aaron

 

[stu40]

Have a read of this;

http/www.fishforum...for-fishshrimp/


Aaron

Thanks