# small daily vs. weekly water changes?



## MrMet (Mar 11, 2010)

Are there any known advantages/disadvantages to doing a smaller, approx. 3% water change daily as opposed to doing a larger 30-40% change weekly?

Thanks for all the help!

Happy Hobbying


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## FSM (Jan 13, 2009)

if you do the math, smaller more frequent water changes use more water to achieve the same result. 3% daily isn't going to do nearly as much as 30 or 40% per week.


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## msnikkistar (Mar 23, 2010)

FSM said:


> if you do the math, smaller more frequent water changes use more water to achieve the same result. 3% daily isn't going to do nearly as much as 30 or 40% per week.


+1

Also, you have to take into account water evaporation. 

I end up having to replace about 1% of my water from evaporation a day. Of course, I use distilled to do this, but you get the point.


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## redfalconf35 (Feb 24, 2008)

msnikkistar said:


> +1
> 
> Also, you have to take into account water evaporation.
> 
> I end up having to replace about 1% of my water from evaporation a day. Of course, I use distilled to do this, but you get the point.


I'm confused... The water evaporates no matter what, so what's it matter if you take out an extra 4% (making a total of 5% removed daily) and replace it all?

@OP: I dunno what would be so bad about doing a small daily water change v. a larger weekly one. If you do a 5% daily change, you get 35% of water cycled through in a week, and the water parameters don't change as drastically as if you yank all 35% at one time and replace it with fresh water. So, i'm with you, unless i'm missing something.


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## Diana (Jan 14, 2010)

Small daily changes can provide more stable conditions compared to weekly or longer intervals. There was a write up at TFH last year about this. 

Lets say you have something increasing @ 5 ppm per day. 
If you do large enough water changes daily then this whatever it is stuff will never get very high. If your daily water changes are not enough to get rid of that 5 ppm then the level of this stuff will keep rising until finally it reaches an equilibrium. 

The same options happen with weekly water changes. 
either the water changes are large enough to remove the week's accumulation of whatever, or else the level keeps rising until the water changes do remove enough of it to hold it stable. The levels can get really high, though, then drop a lot with a large water change. Depending on what substance we are talking about this can have a serious impact on the fish. 
_________________________________________________________________________

If you are setting up an automatic water changer then set it for a daily change. 
Then monitor the results. If they are not what you want, then alter it. Maybe go for twice a day, AM and PM. 

You may end up also doing a weekly vacuum/plant trim/algae swipe/hands on sort of clean up, which will result in more water change.


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## OverStocked (May 26, 2007)

If you remove 5% daily, sure you remove 35% weekly... but... when you remove 5% each day, you remove part of the FRESH water from the day before. Therefore you are never really getting nearly as much crud out or fresh in. 

Tiny water changes added up do not equal singular larger changes.


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## EntoCraig (Jun 7, 2010)

One thing to keep in mind, especially if you are using Tap water or hard water, is that only the water evaporates, none of the mineral hardness does... I think that is what msnikkistar is alluding to with using distilled water. 

In theory I think you are right, If you are removing the same total amount of water daily as you would in a weekly water change you should be okay. Sounds like a lot of work to me though  

However I do have a 1.5 gallon planted tank that I do 2 mini changed a week on instead of just one large water change(if you can call it that)... However this tank is at work where we have distilled water.


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## sewingalot (Oct 12, 2008)

I switched from weekly water changes to small water changes every other day on my smaller tank and couldn't be happier with the results. This is a fry growout tank and I have noticed less accumulation of gunk, faster growth and more fry grow up to be adults.


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## Diana (Jan 14, 2010)

Removing the same mathematical amount daily and weekly will not result in the same amount of benefit to the tank. If you want to do the same waste removal amounts you need to do larger water changes daily to equal the amount of waste removal done with a large once-a-week water change. 

10% WC per day, for example is not the same as 70% once a week, but more like about 40%.

TFH articles were in Nov and Dec. '09. They included charts and water tests to show what the water was like every day for several weeks on each system.


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## EntoCraig (Jun 7, 2010)

sewingalot said:


> I switched from weekly water changes to small water changes every other day on my smaller tank and couldn't be happier with the results. This is a fry growout tank and I have noticed less accumulation of gunk, faster growth and more fry grow up to be adults.


I believe this is common practice for small Fry tanks. I do the same on mine  I find that if I keep the water MEGA clean I see a significant increase in Fry Survival. I would never do the mini water changes on my larger tanks though. That is a lot of water changing time every day!


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## DarkCobra (Jun 22, 2004)

Let's say you have an aquarium with 100ppm of something you don't want.

Do a 50% water change with clean water, and you now have 50ppm; simple enough.

But if you instead do two 25% water changes:

1st change: 100ppm * 0.75 = 75ppm
2nd change: 75ppm * 0.75 = 56.25ppm

Not a huge difference, but you can see it's less effective at removing the unwanted substance. Also, on the second change, you're effectively throwing out 6.25% of the water you just added on the first change, including any conditioners or nutrients you put in that replacement water; so it's also a bit wasteful.

I'd consider the main disadvantage to be the extra labor in doing frequent small changes.

Any advantage to dividing a weekly water change into daily water changes is probably so small as to be unnoticeable. If you have a species sensitive to large water changes, dividing a weekly change into two a week should suffice. I have some Glofish that are killed instantly by 50% water changes, but 25-33% doesn't affect them at all.


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## EntoCraig (Jun 7, 2010)

DarkCobra said:


> Let's say you have an aquarium with 100ppm of something you don't want.
> 
> Do a 50% water change with clean water, and you now have 50ppm; simple enough.
> 
> ...


This is a great example of the effects. Yo can see that the difference is that drastic and could potentially be removing anything you have purposely added into the water. It really does depend entirely on your setup, fish and your desired results...


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## sewingalot (Oct 12, 2008)

EntoCraig said:


> I believe this is common practice for small Fry tanks. I do the same on mine  I find that if I keep the water MEGA clean I see a significant increase in Fry Survival. I would never do the mini water changes on my larger tanks though. That is a lot of water changing time every day!


I think if I had an automatic changer, life would be good. :icon_wink


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## EntoCraig (Jun 7, 2010)

sewingalot said:


> I think if I had an automatic changer, life would be good. :icon_wink


An auto changer on mini tanks would be great! especially Fry rearing tanks. However, I like doing my water changes on my larger tank, that way I can fake a rain storm with a large cold water change and induce spawning in my SA cichlids and a few other species I am keeping.


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## msnikkistar (Mar 23, 2010)

EntoCraig said:


> One thing to keep in mind, especially if you are using Tap water or hard water, is that only the water evaporates, none of the mineral hardness does... I think that is what msnikkistar is alluding to with using distilled water.


Bingo 

If you replace evaporated water, with the tap, your mineral hardness increases.


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## Wasserpest (Jun 12, 2003)

Keep in mind there are many ways to do things, and that each tank is different. Some folks do 50% water changes, others don't change water at all. 

So if someone claims that a certain percentage will not do certain things, take it with a grain of salt. What if there is no accumulation of "bad things" -- whatever they are?

For EI overdosed tanks, by all means do weekly 50% water changes to get things back down to healthy levels. If you don't fertilize that much, 5% daily water changes might be perfectly fine, and whether or not they amount to 30 or 35% weekly isn't really that important.

All depends on your particular tank, stocking levels, dosing routines, plant density, etc. Often, doing larger water changes (daily or weekly) benefits everything, except the monthly water bill.


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## Hoppy (Dec 24, 2005)

For my 2 ripariums I use an automatic water change system that removes about 4 gallons from each tank, each of which contains about 30-35 gallons. The change occurs by adding water slowly at one end of the tank, as water overflows out a drain on the other end of the tank. The drain flows much more slowly than the inlet, so the water level rises an inch or so, then drains back to the set level. This has give me no problems, other than once having to "restart" the siphon for one of the drains. It gives me 8 gallons of water a day to use for my container plantings on my deck, just about the right amount, and lightly fertilized water at that.

I use my system because I'm just too lazy to do real 50% water changes, and because I enjoy having the water level remain the same day after day. For me it is great. For anyone else, it might be a royal pain.


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## EntoCraig (Jun 7, 2010)

Hoppy said:


> For my 2 ripariums I use an automatic water change system that removes about 4 gallons from each tank, each of which contains about 30-35 gallons. The change occurs by adding water slowly at one end of the tank, as water overflows out a drain on the other end of the tank. The drain flows much more slowly than the inlet, so the water level rises an inch or so, then drains back to the set level. This has give me no problems, other than once having to "restart" the siphon for one of the drains. It gives me 8 gallons of water a day to use for my container plantings on my deck, just about the right amount, and lightly fertilized water at that.
> 
> I use my system because I'm just too lazy to do real 50% water changes, and because I enjoy having the water level remain the same day after day. For me it is great. For anyone else, it might be a royal pain.


I would love to see some pictures of this setup! if you can


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## mistergreen (Dec 9, 2006)

Do whatever works for you.

I have 2 small low tech tanks where I don't do water changes. All I do is top off evaporated water with plain tap water. The GH & PH are softer than my high tech tank where 50% is changed weekly. I figure the plants & DOC(dissolved organic carbon) have a major roll in affecting the water column.

Theory and practice are 2 different things in this case.


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## plantbrain (Dec 15, 2003)

You mean there might be other factors than ppm's that influence all this? biggrin:

I think most could give a rat's hind quarter about the cost of the water use.
If cost is really an issue, light would be where to cut those cost.

So what is it about WC's that are relevant to plant and hobbyist in general?
Labor is the biggest factor.

So is it more labor to do 50% say vs 5%? For many, not much, we wait 5 min more to fill/refill, that's all. If you use RO, well then there's limits on the volumes. Many do not use RO though, and those that do, well, it's almost never for the plants really.

Still, the basic question is which is better, 5 daily vs 50% from a management perspective?

50%=> much less labor
50%=> more more efficient removal of anything (this assumes there's a risk to begin with, which IME/IMO, is extremely rare).

I think some of these ideas for small daily WC's come from fish only systems, not planted or fertilized systems. 

WC's add CO2 and more O2 also, so adding a small bit daily or even a large 40-50% daily will help plants.

Still, at the other end, non CO2 planted tanks go years without WC's, and they do quite well.

Less light = more stability and more wiggle room with water changes.
Still, a large one once a week is not that much labor.

Still again......you can set up automated or semi automated systems and then it's even less labor(the real key if the WC is an issue for you, as it's more difficult to automate testing for NO3 etc). I suppose you could use a TDS controller and set that up for automated water changer.

For myself and most, 50% once a week is easier than 5% per day and a lower light/non CO2(or anything that direction method wise). is going to increase flexibility with WC's

Regards, 
Tom Barr


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