beaslbob
Well-Known Member
At my request and promise to behave, the powers that be have restored my posting here.
For those who are fortunate to have missed the past, I have had various FW planted tanks and simple FO marine tanks since 1979. I still have my 55g which has had fish and soft corals for 3-5 years or so. I do not have any success with sps corals so I would seek advice from others for that.
I notice that not too many active posters remain from five years ago so I thought I would reintroduce myself with a discussion of water changes just for your consideration.
Fortunately, water changes are something that can be analyzed with math given a few assumptions. As opposed to more emotional arguments like how would you like to live in a bathtub with no water changes or water changes replace trace elements.
For the following analysis I am assuming something is in the replacement water. So let's call that “something”. Gee how original.
And something in the water is at a certain concentration of galloping elephants.
So this could be anything of any units of concentration. But let's also assume that galloping elephants is a linear measure unlike pH.
So you have a tank with some initial galloping elephants of something. And every so often you do a 10% water change. So after the first change you have 9/10s of the initial remaining. Second is 9/10s of that for 9/10*(9/10). the third (9/10)*(9/10)*(9/10) and so on. So that after sufficient water changes you have unmeasurable initial galloping elephants and the tank totally reflects the galloping elephants of the replacement water.
Simple. And what you usually hear here, at LFSs, in normal conversations and so on.
But now also assume that the tank has a constant change in something so that each day you have more or less galloping elephants. To analyze this case assume the replacement water has no galloping elephants. And to make analysis easier assume water changes are conducted at the same level and interval.
How much something is in the tank just before each water change after enough water changes have been conducted that we cannot measure the difference? In order for that to be true:
The amount of (between water change) change in something must be removed by the water change.
So if you do say 10% water changes, something must be 10 times the change. The water change then lowers the change to 9 times and something builds up again to 10 times just before the next change. 20% 5 times to 4 to 5. 33% 3 times to 2 to 3. etc. Mathematically:
just before water change=(change between water changes)/(fraction of water changes)
If you allow for some of something in the replacement water you combine the two effects:
just before water change=(change between water changes)/(fraction of water changes)+replacement water
If you “tie” the amount of water changes to the water change some interesting (to me anyway) results happen. Like 1%/day, 10%/10 days and so on. In that case:
Just before water change=(daily change*days between water changes)/(fraction of water changes)+replacement water.
Under those assumptions the following occurs:
days_____change__before_after___next
100______100%___100____0_____100
50_______50%_____100__50___100
33_______33%_____100__67___100
20_______20%_____100__80___100
10_______10%_____100__90___100
5_________5%_____100__95___100
1_________1%_____100__99___100
.5________.5%_____100_99.5__100
The limit of a continuous change at the rate of 1%/day you have a continuous 100 galloping elephants.
And to all those figures you add in whatever the concentration is in the replacement water. Both the before and after values are increased by whatever is in the replacement.
For those who are fortunate to have missed the past, I have had various FW planted tanks and simple FO marine tanks since 1979. I still have my 55g which has had fish and soft corals for 3-5 years or so. I do not have any success with sps corals so I would seek advice from others for that.
I notice that not too many active posters remain from five years ago so I thought I would reintroduce myself with a discussion of water changes just for your consideration.
Fortunately, water changes are something that can be analyzed with math given a few assumptions. As opposed to more emotional arguments like how would you like to live in a bathtub with no water changes or water changes replace trace elements.
For the following analysis I am assuming something is in the replacement water. So let's call that “something”. Gee how original.
And something in the water is at a certain concentration of galloping elephants.
So this could be anything of any units of concentration. But let's also assume that galloping elephants is a linear measure unlike pH.
So you have a tank with some initial galloping elephants of something. And every so often you do a 10% water change. So after the first change you have 9/10s of the initial remaining. Second is 9/10s of that for 9/10*(9/10). the third (9/10)*(9/10)*(9/10) and so on. So that after sufficient water changes you have unmeasurable initial galloping elephants and the tank totally reflects the galloping elephants of the replacement water.
Simple. And what you usually hear here, at LFSs, in normal conversations and so on.
But now also assume that the tank has a constant change in something so that each day you have more or less galloping elephants. To analyze this case assume the replacement water has no galloping elephants. And to make analysis easier assume water changes are conducted at the same level and interval.
How much something is in the tank just before each water change after enough water changes have been conducted that we cannot measure the difference? In order for that to be true:
The amount of (between water change) change in something must be removed by the water change.
So if you do say 10% water changes, something must be 10 times the change. The water change then lowers the change to 9 times and something builds up again to 10 times just before the next change. 20% 5 times to 4 to 5. 33% 3 times to 2 to 3. etc. Mathematically:
just before water change=(change between water changes)/(fraction of water changes)
If you allow for some of something in the replacement water you combine the two effects:
just before water change=(change between water changes)/(fraction of water changes)+replacement water
If you “tie” the amount of water changes to the water change some interesting (to me anyway) results happen. Like 1%/day, 10%/10 days and so on. In that case:
Just before water change=(daily change*days between water changes)/(fraction of water changes)+replacement water.
Under those assumptions the following occurs:
days_____change__before_after___next
100______100%___100____0_____100
50_______50%_____100__50___100
33_______33%_____100__67___100
20_______20%_____100__80___100
10_______10%_____100__90___100
5_________5%_____100__95___100
1_________1%_____100__99___100
.5________.5%_____100_99.5__100
The limit of a continuous change at the rate of 1%/day you have a continuous 100 galloping elephants.
And to all those figures you add in whatever the concentration is in the replacement water. Both the before and after values are increased by whatever is in the replacement.
