using sump to reduce nitrates

beaslbob

Well-Known Member
Thought I would post this here for all of you to consider.

We constantly add sumps to lower nitrates (among many many other things.)

Assuming you say double your total volume, nothing else changes, and you are doing the same volume of water change what happens when everything has settled down and the nitrates before each water change is the same?

Ans: it arrives at the same exact value.

What happens it does take longer to arrive at that value but the end point is exactly the same.

Assume you have a system that is increasing 1ppm nitrate per day and you are doing a 10 g water change in a 100g tank every 10 days with 0 nitrate replacement water.

The tank will wind up at the point where the nitrates removed by the water change equals the total nitrate increase between water changes.

Nitrates before water change=replacement water nitrates+(nitrate build up)/(fraction of water changed)

In the example above:

nitrates before water change= (0 nitrates in replacement water)+(1ppm/day*10days/(1/10)=0+10/(1/10)=100ppm

After adding the sump:

The nitrates are still increasing at the same total amount but there is twice the volume. So the daily build up is .5ppm/day

The water change is now 10g/200b=1/20

The tank winds up at:
nitrates before water change=(0 nitrates in replacement water)+(.5ppm/day*10days)/(1/20)=0 +(5ppm)/(1/20)=100ppm

So it does take longer to arrive at the point but the end point in either case is 100ppm
 

snakeblitz33

Well-Known Member
You forget that some nitrate is broken down into nitrogen gas or nitrate is used by some organisms to grow and reproduce- including most soft corals.

There are too many variables for it to be this cut and dry. Using macro algae as the be-all end all of filtration is borderline negligent.
 

beaslbob

Well-Known Member
You forget that some nitrate is broken down into nitrogen gas or nitrate is used by some organisms to grow and reproduce- including most soft corals.

There are too many variables for it to be this cut and dry. Using macro algae as the be-all end all of filtration is borderline negligent.
The purpose of this analysis is to consider water changes alone.
While many things are actually going on, this analysis just considers water changes alone.
 

snakeblitz33

Well-Known Member
So in other words, in a perfect system, all things being equal, with no natural denitrification- sure, in theory your analysis works. In practice, in a real system with adequate biological filtration- no.
 

beaslbob

Well-Known Member
So in other words, in a perfect system, all things being equal, with no natural denitrification- sure, in theory your analysis works. In practice, in a real system with adequate biological filtration- no.
Absolutely. With adequate biological filtration nitrates are unmeasureable.
 
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