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So...your nitrates are high and seem to be going up? How can this be so...you do 10 percent water changes every week like some sort of religious ritual. Well take a look at this chart and perhaps you can figure it out.
Remember that the nitrates in the tank are the result of a measurable ammonia output by the inhabitants. Once the tank has become established, the nitrate production starts somewhat constant (remembering that fish grow, bla bla). So changing a certain amount of the water each week will have a measurable and somewhat constant effect on the nitrate levels...but...if your water change is too small or the frequency wrong, the nitrate level will continue to climb.
Reading the following chart can be a little tricky. The first row is the size of the water change. The second row is the frequency of that water change. The first column on the left is the relative nitrate reading each day (changing to months). In the row that is labeled "Day 1" is the daily rate of nitrate production. If you were to have a reading taken every day just prior to a 100% water change, this would be the nitrate production per day. The daily production is somewhat relative because all the factors of nitrate production can not be accounted for in a straight-line calculation. However, the point being illustrated is still graphically demonstrated by the chart.
If you look at the last row you can note that changing 25% of the water daily produces roughly the same result as changing 50% on a weekly basis. One task being infinitely less demanding than the other.
Understanding that other issues play a role such as consistent water condition being important as opposed to periodic corrections and that some make their water changes based upon personal life style, the chart is meant as a guide. The only truly accurate schedule would be designed based upon proper testing for nitrate levels and adjusting those levels through water changes at appropriate intervals.
amount of change> 50%
25%
10%
frequency of change> monthly
weekly
daily
monthly
weekly
daily
monthly
weekly
daily
measures taken at: measured nitirate> Day 1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Day 2
. . 0.75
. . 1.125
. . 1.35
Day 3
.. . 0.875
. . 1.593
. . 2.115
Day 4
. . 0.937
. . 1.945
. . 2.803
Day 5
. . 0.968
. . 2.208
. . 3.423
Day 6
. . 0.984
. . 2.406
. . 3.980
Day 7
. 1.75
0.992
. 2.625
2.555
. 3.15
4.482
Day 8
. . 0.996
. . 2.666
. . 4.934
Day 9
. . 0.998
. . 2.749
. 5.706
5.341
Day 10
. . 0.999
. . 2.812
. . . Day 11
. . 0.999
. . 2.859
. . 6.036
Day 12
. . 0.999
. . 2.894
. . 6.332
Day 13
. . 0.999
. . 2.920
. . 6.599
Day 14
. 2.625
0.999
. 2.625
2.940
. 5.985
6.839
Day 15
. . 0.999
. . 2.955
. . 7.055
Day 16
. . 0.999
. . 2.966
. . 7.249
Day 17
. . 0.999
. . 2.974
. . 7.424
Day 18
. . 0.999
. . 2.981
. . 7.582
Day 19
. . 0.999
. . 2.985
. . 7.724
Day 20
0.999
2.989
7.851
Day 21
. 3.062
1
. 2.625
2.992
. 8.536
7.966
Day 22
. . 1
. . 2.994
. . 8.069
Day 23
. . 1
. . 2.995
. . 8.162
Day 24
. . 1
. . 2.996
. . 8.246
Day 25
. . 1
. . 2.997
. . 8.321
Day 26
. . 1
. . 2.998
. . 8.389
Day 27
. . 1
. . 2.998
. . 8.450
Month 1
7
3.281
1
10.5
2.625
2.998
12.6
10.832
8.505
Month 2
13.890
3.486
1
36.393
10.492
2.999
65.734
17.940
8.974
Month 3
13.945
3.499
1
37.795
10.497
3
71.761
22.603
8.998
Month 4
13.972
3.499
1
38.846
10.499
3
77.185
25.662
8.999
Month 5
13.986
3.499
1
39.634
10.499
3
82.066
27.670
8.999
Month 6
13.993
3.5
1
40.226
10.499
3
86.459
28.987
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