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Change the water
- Thread starter luiz Claudio
- Start date
Ben":hgc7nkyc said:Larger changes les often are more productive then lots of small changes.
Three 10 gal. changes versus one 30 gal. change for instance, the 30 gal change will remove more nutrients. There is a few articals on this in the library.
This is true if your changing the same volume, changing it all at once is better.
But if your frequency on the smaller changes is high enough that you're still keeping up with the dilution, they lead to more stable water conditions.
So while 3 10 gallon changes vs a 30 gallon change in the same time frame won't dilute as much, a larger number (number depends on how much of your total volume this represents) of 10-15 gallon chages may still allow you to export the same amount of undesirables while not causing as sudden a shift in water chemistry.
Ben":266a6y2m said:
Yep, that's exactly what I mean though. If your asking:
Is it better to change 10% a month or 25% a month, form a dilution presepective the answer's obvious.
heck if your asking is it better to change 20% a month, or 5% a week. (still ~20% in the month) the answer's still obvious.
But how about is it better to change 25% vs. multiple 10% changes in the same time frame.
Wiht one 25% water change you reduce the undesired substnace to 75%. Now with 10% changes over tehe same time period you get:
Only one chage = 90%
Two changes = 81%
Three changes = 73%
So at three changes in the same timeframe we're doign a bit better than a single 25% change. Yes I know that a 30% change instead would beat that, but that's not my point.
My point is that a higher number of smaller changes can net you the same improvements in dilution (at the expense of having changed more water) while maintianing a more stable chemistry as the individual changes are smaller.
I am not suggesting you change the same volume of water over a given time in smaller doses, but rather that changing more volume in smaller doses gives you added stability. You can increase the dilution to be equivalent to whatever dilution rate you want, though it would become impractical to try to use very small (say 10%) changes to get teh same dilution that a single very large (say 50%) change would give you. But if you're doing 50% changes odds are its to reduce a drastic problem, and not part of your standard maintenance.
Now I'm not suggesting 10% as the proper amount, I just chose 10 and 25 % as they were on the graphs.
It's a 3 way balancing act with the factorse being:
-Rate of dilution
-Effort/Cost
-Stability of chemistry
The appropriate balance depends on the situation. For regular maintenance you have to look at all three factors. For reducing something that shouldn't be there in the first place, stability becomes much less of an issue, as you don't want slow changes, you want whatever the problem is reduced more quickly.
In the above example, to get comaparable dilution (3 10% changes vs a 25% change) you would be using 20% more salt and water per unit time. In addition your effort increases rapidly as well. Call it double the effort for 3 10% vs one 25% (just a rough guess).
All of the stuff that applies to dilution applies to replenishment as well.
Couldnt get the link to work but here is some more published data on water changes:
AN ADVANCED AQUARIST SHORT TAKE by D. WADE LEHMANN
Sponsored in part by:
Necessary Maintenance - Water Changes
Proud sponsor of this column
There are few things in this hobby which are static or even thoroughly understood. The effects of regular water changes are no exception. I will illustrate for you exactly why I believe that water changes are an integral part of the regular maintenance on reef tanks and how much should be changed at once.
I constantly hear people say that they have never done a water change on their tanks. I have heard people say just the opposite; that they do very regular water changes. I have seen tanks that look great with both and tanks that look horrible with both - water changes are not a cure-all for everything nor anything specific. That being said, I will say that in my years of reefkeeping experience, almost all tanks that have regular schedules of water changes look the best.
Water changes are a relatively low cost and easily attainable portion of a regular maintenance regime. They help by removing unwanted waste products and possible contaminants. They are also beneficial in the replacement of those nutrients and elements, which are normally consumed in the tank and not readily replaced. I have even seen tanks that use water changes as a sole source of replenishment (no additional supplementation). While that is not feasible for most of us due to time, cost, and headache, it would be ideal.
One key item to be aware of is the dilution effect of water changes. In order for a water change to be useful, you must remove a portion of the water entirely and then replace that portion. If you add new water to the system, then remove the same volume, you are actually reducing the value of your new water significantly due to dilution. In effect, you are removing some of the new water you have just added, although in reality you dilute down the compounds you are trying to remove and then removing a portion of that diluted water (figure 1).
Figure 1 - Diagramatic representation of two forms of water changes. (Top) Removal followed by new water replacement. (Bottom) Addition of new water followed by removal of equal volume. N represents a contaminant concentration.
Automation
There are different methods for replacement of aquarium water with varying degrees of ease. Most people drain their sumps and replace the old tank water with new water using a siphon or scoop and a few buckets. Some have elaborate systems of valves and plumbing as an integral part of their system that allow simultaneous removal and replenishment from two differing areas of the setup.
I perform mostly regular bi-weekly water changes with a 30g mixing trash can, a Mag 7 pump, and some tubing. I run new water into the sump while simultaneously diverting the main return line into a second 30g waste container without stopping the return pump. This allows for maximal ease and due to the large volume of my sump, little to no mixing of new and old water prior to disposal.
Automation, in general, allows for an easier more hassle free water exchange, which as we all know makes it an easier and more readily completed chore.
How much should I change?
The portion changed, or percent of system volume replaced, is a critical issue when talking about removal of possible toxicants and toxins, and replacement of valuable elements and nutrients.
Consider this hypothetical situation. You are cleaning up around the tank, when someone walks by and accidentally spills a cleaning solution into your tank. What do you do? Once the initial panic subsides, you realize that you need to perform some water changes. The chemical, luckily, is not very toxic, but it is still a concern and using activated carbon and a skimmer will not remove it. So, you have a bucket of prepared saltwater… is it enough?
Figure 3 illustrates the remaining fraction (in %) of the compound after water changes of varying sizes. Ten, twenty, and thirty percent changes have differing effectiveness in removal of the cleaner.
Figure 3 - 10, 20, 30, and 50% water changes and their dilutory effects. Note the effectiveness of larger % changes. The half-life of a hypothetical compound in the aquarium (t1/2 or time in changes to remove half) occurs at 8, 3, 2, 1 changes respectively.
If you were to perform 10% changes on your tank to remove the cleaner, it would take you 23 changes of water to get the level of the compound in the tank down to less than 10% (9.85%) of the starting concentration. Likewise at 20% and 30% volume changed, it would take you 11 and 7 water changes to bring the level down to 8.6% and 8.2% of the starting concentration respectively. While I would not recommend a 50% water volume change for most tanks, it is very much more effective in eliminating the original spill of cleaner. It would take only 4 water changes to bring the level down to below 10% (6%) of the original concentration.
Proud sponsor of this column
The risk, at 50% water volume changed, typically comes from shock and stress to the occupants of the tank due to salinity, temperature, and other physical-chemical differences that occur between old tank water and new water. For this reason, unless it is a true emergency situation, I do not promote changing 50% of the water volume.
The case of the 10% water change is also negative. While 10% is better than no actual volume changed regularly, it will take a great deal of time to remove any potential threats and replace those compounds that are valuable to the tank. In figure 4, it illustrates 10% changes and the effect of such a small change. Thirty consecutive water changes of 10% total volume means that you will still be left with almost 5% of the starting concentration of contaminants. In line with that consideration is that fact that at best, 30 water changes will take half a year to complete at more than one per week.
Figure 4 - Illustration of the % remaining and the actual parts per million (mg/liter) remaining assuming 2ppm addition of a toxicant.
The effects of water changes are exemplified in cases where people have underpowered skimmers, no skimmer at all, or very small tanks. Changing water on a regular basis can have the same effect as running a skimmer at removal of organic wastes, although the lack of a skimmer will allow for more bacterial decomposition of the compounds (less real-time removal) prior to elimination.
After considering the result of changing varying percentages of water volume, I highly suggest 20 or 30% water changes, performed on a semi-regular basis. Usually every 2 to 3 weeks or whenever conditions in the tank appear to change or the water turns somewhat yellow due to the organic acids from decomposition building up.
Water change volume table
Water Change Volumes (in gallons) Per Tank Size
Tank Size in gallons
Estimated Actual Volume
Estimated Water for 20%
Estimated Water for 30%
10
7
1.4
2.1
20
14
2.8
4.2
29
20.3
4.1
6.1
40
28
5.6
8.4
55
38.5
7.7
11.6
75
52.5
10.5
15.8
90
63
12.6
18.9
120
84
16.8
25.2
125
87.5
17.5
26.3
150
105
21
31.5
185
129.5
25.9
38.9
300
210
42
63
The table gives the most common size tanks and their nominal and estimated volumes in gallons. The estimated volume is 70% of the maximal tank volume as water assuming that sand, rock, and various forms of life occupy the remaining space. Twenty and thirty percent change volumes (in gallons) are shown.
To access our Short Take forum to discuss this article, click here
Copyright 2003 Advanced Aquarist's Online Magazine
AN ADVANCED AQUARIST SHORT TAKE by D. WADE LEHMANN
Sponsored in part by:
Necessary Maintenance - Water Changes
Proud sponsor of this column
There are few things in this hobby which are static or even thoroughly understood. The effects of regular water changes are no exception. I will illustrate for you exactly why I believe that water changes are an integral part of the regular maintenance on reef tanks and how much should be changed at once.
I constantly hear people say that they have never done a water change on their tanks. I have heard people say just the opposite; that they do very regular water changes. I have seen tanks that look great with both and tanks that look horrible with both - water changes are not a cure-all for everything nor anything specific. That being said, I will say that in my years of reefkeeping experience, almost all tanks that have regular schedules of water changes look the best.
Water changes are a relatively low cost and easily attainable portion of a regular maintenance regime. They help by removing unwanted waste products and possible contaminants. They are also beneficial in the replacement of those nutrients and elements, which are normally consumed in the tank and not readily replaced. I have even seen tanks that use water changes as a sole source of replenishment (no additional supplementation). While that is not feasible for most of us due to time, cost, and headache, it would be ideal.
One key item to be aware of is the dilution effect of water changes. In order for a water change to be useful, you must remove a portion of the water entirely and then replace that portion. If you add new water to the system, then remove the same volume, you are actually reducing the value of your new water significantly due to dilution. In effect, you are removing some of the new water you have just added, although in reality you dilute down the compounds you are trying to remove and then removing a portion of that diluted water (figure 1).
Figure 1 - Diagramatic representation of two forms of water changes. (Top) Removal followed by new water replacement. (Bottom) Addition of new water followed by removal of equal volume. N represents a contaminant concentration.
Automation
There are different methods for replacement of aquarium water with varying degrees of ease. Most people drain their sumps and replace the old tank water with new water using a siphon or scoop and a few buckets. Some have elaborate systems of valves and plumbing as an integral part of their system that allow simultaneous removal and replenishment from two differing areas of the setup.
I perform mostly regular bi-weekly water changes with a 30g mixing trash can, a Mag 7 pump, and some tubing. I run new water into the sump while simultaneously diverting the main return line into a second 30g waste container without stopping the return pump. This allows for maximal ease and due to the large volume of my sump, little to no mixing of new and old water prior to disposal.
Automation, in general, allows for an easier more hassle free water exchange, which as we all know makes it an easier and more readily completed chore.
How much should I change?
The portion changed, or percent of system volume replaced, is a critical issue when talking about removal of possible toxicants and toxins, and replacement of valuable elements and nutrients.
Consider this hypothetical situation. You are cleaning up around the tank, when someone walks by and accidentally spills a cleaning solution into your tank. What do you do? Once the initial panic subsides, you realize that you need to perform some water changes. The chemical, luckily, is not very toxic, but it is still a concern and using activated carbon and a skimmer will not remove it. So, you have a bucket of prepared saltwater… is it enough?
Figure 3 illustrates the remaining fraction (in %) of the compound after water changes of varying sizes. Ten, twenty, and thirty percent changes have differing effectiveness in removal of the cleaner.
Figure 3 - 10, 20, 30, and 50% water changes and their dilutory effects. Note the effectiveness of larger % changes. The half-life of a hypothetical compound in the aquarium (t1/2 or time in changes to remove half) occurs at 8, 3, 2, 1 changes respectively.
If you were to perform 10% changes on your tank to remove the cleaner, it would take you 23 changes of water to get the level of the compound in the tank down to less than 10% (9.85%) of the starting concentration. Likewise at 20% and 30% volume changed, it would take you 11 and 7 water changes to bring the level down to 8.6% and 8.2% of the starting concentration respectively. While I would not recommend a 50% water volume change for most tanks, it is very much more effective in eliminating the original spill of cleaner. It would take only 4 water changes to bring the level down to below 10% (6%) of the original concentration.
Proud sponsor of this column
The risk, at 50% water volume changed, typically comes from shock and stress to the occupants of the tank due to salinity, temperature, and other physical-chemical differences that occur between old tank water and new water. For this reason, unless it is a true emergency situation, I do not promote changing 50% of the water volume.
The case of the 10% water change is also negative. While 10% is better than no actual volume changed regularly, it will take a great deal of time to remove any potential threats and replace those compounds that are valuable to the tank. In figure 4, it illustrates 10% changes and the effect of such a small change. Thirty consecutive water changes of 10% total volume means that you will still be left with almost 5% of the starting concentration of contaminants. In line with that consideration is that fact that at best, 30 water changes will take half a year to complete at more than one per week.
Figure 4 - Illustration of the % remaining and the actual parts per million (mg/liter) remaining assuming 2ppm addition of a toxicant.
The effects of water changes are exemplified in cases where people have underpowered skimmers, no skimmer at all, or very small tanks. Changing water on a regular basis can have the same effect as running a skimmer at removal of organic wastes, although the lack of a skimmer will allow for more bacterial decomposition of the compounds (less real-time removal) prior to elimination.
After considering the result of changing varying percentages of water volume, I highly suggest 20 or 30% water changes, performed on a semi-regular basis. Usually every 2 to 3 weeks or whenever conditions in the tank appear to change or the water turns somewhat yellow due to the organic acids from decomposition building up.
Water change volume table
Water Change Volumes (in gallons) Per Tank Size
Tank Size in gallons
Estimated Actual Volume
Estimated Water for 20%
Estimated Water for 30%
10
7
1.4
2.1
20
14
2.8
4.2
29
20.3
4.1
6.1
40
28
5.6
8.4
55
38.5
7.7
11.6
75
52.5
10.5
15.8
90
63
12.6
18.9
120
84
16.8
25.2
125
87.5
17.5
26.3
150
105
21
31.5
185
129.5
25.9
38.9
300
210
42
63
The table gives the most common size tanks and their nominal and estimated volumes in gallons. The estimated volume is 70% of the maximal tank volume as water assuming that sand, rock, and various forms of life occupy the remaining space. Twenty and thirty percent change volumes (in gallons) are shown.
To access our Short Take forum to discuss this article, click here
Copyright 2003 Advanced Aquarist's Online Magazine
Seriously, water change opinions are like tanks. Everybody has got one. I go with about 30% every one or two weeks. I have a small tank though, with no really sensative animals. The polyps don't seem to mind the change at all, and none of the corals close up, even during the change. One thing that I do do is to drain the new water into the tank through a very small hose, which I hope means tht everything in the tank isn't being clobbered with pH and salinity shifts in a 60 second span.
The cost of the water changes in my tank is about 2 or three bucks, so, for us small tank guys, there's no financial excuse not to change water.
As for 10 percent three times, 30 percent once, etc., it's all about what's convenient for me. 10% 3 times in a week or 30 percent once in a week I think won't cause much difference on most tanks.
The cost of the water changes in my tank is about 2 or three bucks, so, for us small tank guys, there's no financial excuse not to change water.
As for 10 percent three times, 30 percent once, etc., it's all about what's convenient for me. 10% 3 times in a week or 30 percent once in a week I think won't cause much difference on most tanks.
I'd say whatever works best for your tank.
IMHO there are too many variables from tank to tank.
Just a f'rinstance, I've got a 15High that I change 5 gal every 2 weeks...no issues with it and everything is healthy..no bad algae at all and good coralline growth. However, the only critters are my Damsel, 4 hermits, about 3lbs live rock with about 8-9 shrooms, 2 snails and tons of pods.
If this were a full blown nano reef, or if I had a larger bioload naturally I'd change the amt/schedule of my changes.
Test your params...find what works best for you and maintain the schedule diligently.
Just my $.02, your mileage may vary
IMHO there are too many variables from tank to tank.
Just a f'rinstance, I've got a 15High that I change 5 gal every 2 weeks...no issues with it and everything is healthy..no bad algae at all and good coralline growth. However, the only critters are my Damsel, 4 hermits, about 3lbs live rock with about 8-9 shrooms, 2 snails and tons of pods.
If this were a full blown nano reef, or if I had a larger bioload naturally I'd change the amt/schedule of my changes.
Test your params...find what works best for you and maintain the schedule diligently.
Just my $.02, your mileage may vary
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