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An
article by George J. Reclos
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OK,
you are religiously doing your water changes and you feel you have
done your duty. However there is still a large amount of old water
in your tank. How much? The tables below give you the answer. The
blue square at the top left corner is the hypothetic amount of water
you change in every water change. The yellow row is the weeks (or
days if you do daily changes) after we start counting. At day 0 we
assume that all the water in the tank was fresh. The red column
shows you the age of the water present in your tank after each
change. Thus, in the 10% water change table we can see that after 4
changes (a month), you have 66% of water aged 4 weeks.
What's
more, after the 7th water change, there is still a 48% of water aged
7 weeks - almost half your water volume. The cells shaded with a
light pink color indicate the percentage water which is over a month
old. As you can see, with 50% weekly changes there is almost no
water aged over 6 weeks, while at 80% weekly changes there is almost
no water aged over 4 weeks (less than 2%). I hope these tables will
help you to evaluate the size of your water changes. The idea to
build these tables was given to me by an article of D.A.Boruchowitz
which appeared in TFH, issue #530. |
|
10% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
|
1 |
90,00 |
9,00 |
9,00 |
9,00 |
9,00 |
9,00 |
9,00 |
|
2 |
|
81,00 |
8,10 |
8,10 |
8,10 |
8,10 |
8,10 |
|
3 |
|
|
72,90 |
7,29 |
7,29 |
7,29 |
7,29 |
|
4 |
|
|
|
65,61 |
6,56 |
6,56 |
6,56 |
|
5 |
|
|
|
|
59,05 |
5,90 |
5,90 |
|
6 |
|
|
|
|
|
53,14 |
5,31 |
|
7 |
|
|
|
|
|
|
47,83 |
|
20% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
20 |
20 |
20 |
20 |
20 |
20 |
20 |
|
1 |
80 |
16 |
16 |
16 |
16 |
16 |
16 |
|
2 |
|
64 |
12,8 |
12,8 |
12,8 |
12,8 |
12,8 |
|
3 |
|
|
51,2 |
10,24 |
10,24 |
10,24 |
10,24 |
|
4 |
|
|
|
40,96 |
8,19 |
8,19 |
8,19 |
|
5 |
|
|
|
|
32,77 |
6,55 |
6,55 |
|
6 |
|
|
|
|
|
26,21 |
5,24 |
|
7 |
|
|
|
|
|
|
20,97 |
|
30% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
|
1 |
70 |
21 |
21 |
21 |
21 |
21 |
21 |
|
2 |
|
49 |
14,7 |
14,7 |
14,7 |
14,7 |
14,7 |
|
3 |
|
|
34,3 |
10,29 |
10,29 |
10,29 |
10,29 |
|
4 |
|
|
|
24,01 |
7,20 |
7,20 |
7,20 |
|
5 |
|
|
|
|
16,81 |
5,04 |
5,04 |
|
6 |
|
|
|
|
|
11,76 |
3,53 |
|
7 |
|
|
|
|
|
|
8,24 |
|
40% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
40 |
40 |
40 |
40 |
40 |
40 |
40 |
|
1 |
60 |
24 |
24 |
24 |
24 |
24 |
24 |
|
2 |
|
36 |
14,4 |
14,4 |
14,4 |
14,4 |
14,4 |
|
3 |
|
|
21,6 |
8,64 |
8,64 |
8,64 |
8,64 |
|
4 |
|
|
|
12,96 |
5,18 |
5,18 |
5,18 |
|
5 |
|
|
|
|
7,78 |
3,11 |
3,11 |
|
6 |
|
|
|
|
|
4,67 |
1,87 |
|
7 |
|
|
|
|
|
|
2,80 |
|
50% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
50 |
50 |
50 |
50 |
50 |
50 |
50 |
|
1 |
50 |
25 |
25 |
25 |
25 |
25 |
25 |
|
2 |
|
25 |
12,5 |
12,5 |
12,5 |
12,5 |
12,5 |
|
3 |
|
|
12,5 |
6,25 |
6,25 |
6,25 |
6,25 |
|
4 |
|
|
|
6,25 |
3,13 |
3,13 |
3,13 |
|
5 |
|
|
|
|
3,13 |
1,56 |
1,56 |
|
6 |
|
|
|
|
|
1,56 |
0,78 |
|
7 |
|
|
|
|
|
|
0,78 |
|
80% |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
fresh |
80 |
80 |
80 |
80 |
80 |
80 |
80 |
|
1 |
20 |
16 |
16 |
16 |
16 |
16 |
16 |
|
2 |
|
4 |
3,2 |
3,2 |
3,2 |
3,2 |
3,2 |
|
3 |
|
|
0,8 |
0,64 |
0,64 |
0,64 |
0,64 |
|
4 |
|
|
|
0,16 |
0,13 |
0,13 |
0,13 |
|
5 |
|
|
|
|
0,03 |
0,03 |
0,03 |
|
6 |
|
|
|
|
|
0,01 |
0,01 |
|
7 |
|
|
|
|
|
|
0,00 |
|
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