Found this on another forum, thought everyone would benefit from reading this.
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We all test our water. We all read the results. Do we ever stop to think about what they mean to you and your fish?
General maintenance suggests you change on average 20% of the water from your tank every week. Well looking at some results and doing some simple math, 20% is clearly not enough. In fact 50% a week is still not enough.
Below you will see a simple equation that shows how nitrates build up in a non planted tank. We will be conservative and say the tank is lightly stocked so on average the nitrates only build up to 10 ppm each week. In most cases this number is very underestimated
10ppm - one week after a 100% water change.
20% water change - multiply .20 times 10 =s 2ppm subtract that from 10.
8ppm - after 20% water change. Now add 10 ppm for the next week.
18ppm - 2 weeks after 100% water change
20% water change - multiply .20 times 18 =s 3.6ppm subtract that from 18.
14.4ppm - after 20% water change. Now add 10ppm for the next week.
24.4ppm - 3 weeks after 100% water change.
20% water change - multiply .20 times 24.4 =s 4.8ppm subtract that from 24.4
19.6ppm - after 20% water change. Now add 10ppm for the next week.
29.6ppm - after 1 month.
It's very easy to see the pattern of constant gain of the nitrate levels. Even if you do the same math with 50% water changes it quickly gets up to a little over 19ppm, and then keeping up the 50% water changes every week it slowly keeps getting higher and higher.
I guess the point to all this is to show that every now and then we need to (over the coarse of a couple of days) do a 100% water change. Just to keep the levels down.
The math looks even worse if you add the numbers and figure in a missed week where no water changes were done and extra water changes were never done to make up for it.
I would like to add that this is a very good reason to keep live plants, but please keep in mind that plants are still no substitute for water changes.
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We all test our water. We all read the results. Do we ever stop to think about what they mean to you and your fish?
General maintenance suggests you change on average 20% of the water from your tank every week. Well looking at some results and doing some simple math, 20% is clearly not enough. In fact 50% a week is still not enough.
Below you will see a simple equation that shows how nitrates build up in a non planted tank. We will be conservative and say the tank is lightly stocked so on average the nitrates only build up to 10 ppm each week. In most cases this number is very underestimated
10ppm - one week after a 100% water change.
20% water change - multiply .20 times 10 =s 2ppm subtract that from 10.
8ppm - after 20% water change. Now add 10 ppm for the next week.
18ppm - 2 weeks after 100% water change
20% water change - multiply .20 times 18 =s 3.6ppm subtract that from 18.
14.4ppm - after 20% water change. Now add 10ppm for the next week.
24.4ppm - 3 weeks after 100% water change.
20% water change - multiply .20 times 24.4 =s 4.8ppm subtract that from 24.4
19.6ppm - after 20% water change. Now add 10ppm for the next week.
29.6ppm - after 1 month.
It's very easy to see the pattern of constant gain of the nitrate levels. Even if you do the same math with 50% water changes it quickly gets up to a little over 19ppm, and then keeping up the 50% water changes every week it slowly keeps getting higher and higher.
I guess the point to all this is to show that every now and then we need to (over the coarse of a couple of days) do a 100% water change. Just to keep the levels down.
The math looks even worse if you add the numbers and figure in a missed week where no water changes were done and extra water changes were never done to make up for it.
I would like to add that this is a very good reason to keep live plants, but please keep in mind that plants are still no substitute for water changes.
I'm a big advocate of the drip system. It works wonderfully for me.