# Right amount of water changed?



## Krishs Bettas (20 Nov 2010)

Hi everyone,

My tank is  60 litres. I am currently changing 10 litres a week. I was wondering if it is a good amount to change or is it too much of a water change?


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## Garuf (20 Nov 2010)

Too little. 30l or more would be better.


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## Ed Seeley (20 Nov 2010)

The amount of water you change depends entirely on what kind of tank you are running.  My current tank with Tangayikans only gets 10-20% water changes every few weeks whereas when I was running the same tank with EI, high planting and CO2 injection Is changes closer to 50% each week at first.  As the tank matures you can reduce this but be ready to increase water change amounts and frequency if you have problems.

Also if you're not injecting CO2 some people reduce the water changes so that they don't lose the CO2 generated in the tank and have varying CO2 levels.


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## ColinTomson (1 Dec 2010)

As many advices I believe that is better to change between 30 or 40 % of the wtare once a week


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## nry (1 Dec 2010)

As Ed says, it depends on the tank.  EI and similar methods suggest a weekly 50% water change.  If you're running low tech etc. then this 50% change isn't required.

You could even consider half dosing EI and doing a fortnightly 50% change, or a weekly 25% change...it can all be played around with to suit.


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## ColinTomson (3 Dec 2010)

"a fortnightly 50% change, or a weekly 25% change"
... something new for me ...
And wouldn't be so frequent and lot watering changing?!
And may be depends from what kind of fishesh and plants you have


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## Krishs Bettas (3 Dec 2010)

Thanks guys for your tips I think I might do 2 25% changes a week then.


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## idris (7 Jan 2011)

My new tank will be 225L, and hopefully will be both moderately planted and moderately stocked. I am considering CO2 and I haven't really got my head round fertilizers/nutrients/etc yet, but that's all TBC.

My old tank was 60L, and whilst it had plants, could not be thought of as a planted tank. I got quite lax about water changes and ended up doing 50% water changes about once every 2 months. Far from ideal but no fish died in the making of this film.  
So when I read about 50% weekly water changes I am filled with a little horror.   

Prior to reading of such water changes, I was under the impression that larger tanks (to a degree) took less work.
Are higer levels of water changes required for heavily planted tanks?
And _considering the length of a piece of string_, roughly what sort of water changes should I be expecting?


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## nry (7 Jan 2011)

50% changes are suited to those tanks using full EI dosing, high light and CO2.  If you have lower light, don't dose full or any EI, then you can drop the water change amount and frequency.  It is only 50% weekly on EI to bring the fertiliser ppm down to a low level to 'reset' things and then start again.

Larger tanks have a more stable environment usually, but for EI size doesn't really matter so far as I am aware.

Low light/low ferts etc. and you could happily do 25% once a month or once every two months.


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## dw1305 (7 Jan 2011)

Hi all,


> Prior to reading of such water changes, I was under the impression that larger tanks (to a degree) took less work.
> Are higer levels of water changes required for heavily planted tanks?


 As Ed says it really depends upon how you manage your tanks. Diana Walstad's original suggestion for planted low tech. tanks (with a nutritious substrate) was that you didn't need to change any water, just top up when the water level fell. Conversely the "EI method" uses the 50% water change to "re-set" the tank every week, before the new fertilisers are dosed. Tank size is also relevant (if you don't use EI), as you can get away with a more lax water changing regime with larger tanks.  

Personally I will differ from most of the other posters on this forum as I both practice nutrient depletion and change about 10 - 25% of the tank water most days on all tanks under 100 litres. 

cheers Darrel


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## idris (7 Jan 2011)

Phew!


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## Kosh42-EFG (16 Jan 2011)

Another thing to consider is the chemistry of the water you're putting into the tank compared to what it settles at? 

I top up with filtered mains water. Due to the hight CO2 content of this, it meant that if I do a 50% change in one go, the pH drops by over 1.2 and takes most of a day to reach equilibrium. This is one of the reasons I only do smaller changes in my tanks.

I also don't add carbon and add EI at about 20% strength, so it's not an issue for me.


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## ceg4048 (17 Jan 2011)

nry said:
			
		

> ...It is only 50% weekly on EI to bring the fertiliser ppm down to a low level to 'reset' things and then start again..





			
				dw1305 said:
			
		

> the "EI method" uses the 50% water change to "re-set" the tank every week, before the new fertilisers are dosed



Once again, for the umpteenth time, it's necessary to clarify that large water changes, particularly those that involve EI dosed tanks, have nothing to do with "re-setting" the tank of fertilizer. This misconception is one of the more egregious warping of the truth, which only serves to generate more myths and illusions. 

EI, or PMDD, or any eutrophic dosing system does not really care how often or what percentage water change is performed.

The primary purpose of the water change is to rid the tank of accelerated buildup of organic waste. Organic waste buildup has several negative effects as follows:

1) High organic waste increases the Biochemical Oxygen Demand (BOD). 
The BOD can be thought of as the amount of dissolved oxygen required by aerobic (oxygen using) micro-organisms to break down organic waste present in that body of water at give temperature over a unit time period. Therefore, if there is a lot of organic waste present in that body of water, the demand for Oxygen by those micro-organisms is high. Oxygen is a precious commodity in the tank. This should not require an explanation. Plants consume oxygen and they do not produce Oxygen at night. As a result, high levels of organic waste has the effect of micro-organisms and plant competing with fish for Oxygen.

2) Organic waste, gets broken down into it's biological and chemical constituents. One of these constituents is NH3/NH4 (ammonia/ammonium). Another is NO2 (nitrite). Therefore, high levels of organic waste means that high levels of ammonia and nitrite will be produced. This is the same effect as overstocking.

3) Organic waste buildup in a tank has the effect of adding to the thickness of the biofilm by adhering to the plant leaves, thereby blocking gas exchange and impeding nutrient/CO2 uptake by the leaves.

The cumulative effect of these three factors is that fish health can suffer due to hypoxia, anaerobic micro-organism production increase (and their byproducts are unhealthy), fish suffer toxicity due to ammonia/nitrite, plant nutrition suffers due to inefficient nutrient/CO2 uptake and the risk of algal blooms resulting from these condition increases, especially if the lighting is high.

Enriching the tank with CO2, which causes a need for higher nutrient levels, results in higher growth rates and in higher rates of organic waste production. People still haven't figured out that plants produce waste, just like fish do. When you feed your fish more they produce more faeces, CO2 and urine right? Well feeding the plants more also causes them to produce more waste. Depending on the amount of CO2 enrichment there may be 300% to 1000% increase in organic waste production.

Imagine if your fish produce 300% to 1000% increase in faeces and urine. Would you want to do more water changes? The correct answer is YES.

THAT is why EI and other eutrophic dosing schemes elect to do higher levels of water changes. This so-called "re-setting" is just a convenient coincidence that makes the calculations easier. It is also a convenient reality to convince those people, who are paranoid about nutrients, that the levels of nutrients will not rise above a certain level.

But we should not stray from the path. If you feed living things more often then they will grow faster and produce more waste. It's that simple. The problem here is that The Matrix teaches us to fear nutrients and to think of them as dangerous chemicals to be controlled instead of teaching us that they are FOOD.

Therefore as Ed quite rightly pointed out, the amount of water you change should not be ascribed some dogmatic value, but should be considered within the context of how much CO2 and nutrients are being fed and within the context of the factors discussed above, as well as how much time the hobbyist has available for the water change. 

Cheers,


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## dw1305 (17 Jan 2011)

Hi all,


> 1) High organic waste increases the Biochemical Oxygen Demand (BOD).
> The BOD can be thought of as the amount of dissolved oxygen required by aerobic (oxygen using) micro-organisms to break down organic waste present in that body of water at give temperature over a unit time period. Therefore, if there is a lot of organic waste present in that body of water, the demand for Oxygen by those micro-organisms is high. Oxygen is a precious commodity in the tank. This should not require an explanation. Plants consume oxygen and they do not produce Oxygen at night. As a result, high levels of organic waste has the effect of micro-organisms and plant competing with fish for Oxygen.
> 
> 2) Organic waste, gets broken down into it's biological and chemical constituents. One of these constituents is NH3/NH4 (ammonia/ammonium). Another is NO2 (nitrite). Therefore, high levels of organic waste means that high levels of ammonia and nitrite will be produced. This is the same effect as overstocking.
> ...


I agree with all of the above statements, they are some of the most important factors in successful fish keeping, but in that case you would not actually need to change the water at all with EI, just have a very extensive "vacuum", filter clean and then run carbon or a diatomaceous filter pad in your filter (to remove the DOC). 



> Once again, for the umpteenth time, it's necessary to clarify that large water changes, particularly those that involve EI dosed tanks, have nothing to do with "re-setting" the tank of fertilizer. This misconception is one of the more egregious warping of the truth, which only serves to generate more myths and illusions.


I'll stick my my original quote. It may not be the only, or indeed the primary, reason for the water change, but the water change will have the effect of diluting the residual ions on the tank water. Whether you are worried about the levels of residual ions/nutrients/fertilisers in your tank water is another issue.  

You could use a conductivity meter to give you a measure of the total solutes from week to week, but not which salts they are. Short of having some very expensive lab. equipment there is no way of knowing which (if any) ions are accumulating in the water. 

cheers Darrel


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## ceg4048 (17 Jan 2011)

dw1305 said:
			
		

> ..I agree with all of the above statements, they are some of the most important factors in successful fish keeping, but in that case you would not actually need to change the water at all with EI, just have a very extensive "vacuum", filter clean and then run carbon or a diatomaceous filter pad in your filter (to remove the DOC).


Yes, if one had some elaborate way of ensuring DOC removal then you would not need to do the water changes. But most people do not have a means of doing this, and EI is all about simplicity and low cost, so DOC removal is most easily and least expensively accomplished by changing the water.



			
				dw1305 said:
			
		

> I'll stick my my original quote. It may not be the only, or indeed the primary, reason for the water change, but the water change will have the effect of diluting the residual ions on the tank water. Whether you are worried about the levels of residual ions/nutrients/fertilisers in your tank water is another issue.


That is indeed the point. EI does not really care about residual ion levels. If EI were only concerned about residual levels then the dosing program would look very different. It would be a simple matter to simply stop dosing for a period of time, allow the levels to fall, and after that period, resume the dosing. This would ensure that the levels don't build.  There are other ways, such as reducing the dosing after an initial value so that the levels only ever approach some asymptotic level, but again these are all too elaborate and complicated. The main point is to avoid toxicity due to DOC buildup. Once this is achieved then the ion levels are a distant secondary issue.

Again, people become hysterical about ion levels regarding EI and they miss the most important issue of clean water. Instead of associating large water changes with eutrophic dosing, we need to associate the water change with increased health of flora and fauna. In the EI non-CO2 method, water changes are nil, and this works brilliantly. The focus should therefore be that the more you feed your plants the more you need to change the water because that water gets dirtier. Also, folks need to understand that the maintenance isn't only limited to water changes. The more you feed your plants the faster they grow, and the more trimming is required, and the more filter cleaning is required. So eutrophic dosing requires more of everything, not just water changes. There is an entire spectrum of maintenance levels and the hobbyist should decide what level of work he/she is prepared to do. But it needs to be understood in the proper context because the nutrient resetting is actually the least of the worries.

Cheers,


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## nry (17 Jan 2011)

I guess my memory is out of date then, as I recall reading about EI 'back in the day' and the 50% water change which was (in my head) said to be done to reset the tank in respect of the ferts added.


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## nry (17 Jan 2011)

Which is pretty much what this page reads like to me:

http://www.jsctech.co.uk/theplantedtank/EI.htm

"Basically the aquarist doses the tank with a slight excess of nutrients throughout the week to prevent anything from running out and does a large water change at the end of the week to prevent anything from building up."


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## ceg4048 (18 Jan 2011)

Yes, that is absolutely correct. Water change accomplishes this. As I mentioned, it is a convenience, but is not the primary goal. Few EI articles even the original, will touch this topic because it is much too complicated an issue. The articles are all about "How to". Again, you have to remember the history and context in which the article was written. Just about everyone was paranoid about nutrients. So here was a simple scheme that provides all the nutritional requirements for plants but yet does not allow all those nasty algae causing toxic nutrients to build up in your tank.

I mean, has it occurred to you how to reconcile Barr's Non-CO2 method of zero water changes with the statement you quoted? How do you address nutrients building up in those tanks?

If you don't understand the origin or the fundamental truth of an issue then you're bound to be confused by variations on the theme. The truth is that it is the combination of light and CO2 that drives everything. Adding CO2 to the tank shifts the metabolism of the plants immediately into overdrive and increases the production of waste, which means that the waste production exceeds the rate of the tank system to detoxify.

This is a much more important issue than nutrient buildup. We know now that neither algae nor toxicity are correlated to our level of nutrient dosing, so why would resetting have such a high priority?

This is not to say that the tank system can sustain an infinite level of nutrient buildup. NO3 has some toxic level, even if that level is very high, so it would have to be controlled. What I'm saying is that the underlying principle contained in that statement you quoted is not based solely on the necessity to control the tank nutrient levels. The procedure kills two birds with one stone, but the most important bird is the one less well understood.

Cheers,


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## nry (18 Jan 2011)

All I'm trying to put across is how people can be confused by what seems like a simple statement, and not everyone will read further than that and end up giving that 'advice' to others and the 'myth' perpetuates


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## ceg4048 (18 Jan 2011)

Yep, that is true mate, but that's our nature.
Have you ever seen the Monty Python classic "Life of Brian"?
There's a scene where Brian is escaping from the palace guards and a group of people decide to follow his teachings. As he escapes, he drops a shoe and his water gourd.
Half the people agree that the dropped shoe is a sign from heaven and decide to 'follow the shoe". The other half decide that the gourd is more important sign from heaven and they decide to 'follow the gourd".

Now, the idea of resetting the tank nutrient level isn't wrong or deceptive. The concept is absolutely valid and it's an idea that's easy to remember and which serves it's purpose. Imagine trying to explain BOD and biofilm in two sentences. Not happening. I'm just trying to dissuade people from "following the reset" because there is a more fundamental issue to consider when deciding how to manage a CO2 enriched tank. The 50% reset is a good reference, but it was not carved in granite pre-ordained by Moses as he descended from the mountaintop.

The object lesson is that if the OP decided that he didn't want to do a 50% weekly change then it's better if he understands the ramifications of water changes and the consequences of his decision, in order to take appropriate steps.

Having the understanding that the buildup of waste is by far, more of a problem than nutrient buildup is critical in logically arriving at the next conclusion that less waste would be generated by a lower nutrient dosing, that a lower nutrient dosing should be accompanied a lower CO2 injection and that finally, a lower lighting level is consistent/compatible with lower CO2 enrichment.

So we are not required to blindly dose the baseline EI values and then become depressed that we have to do large water changes. All these values can be modulated to suit our ability to perform maintenance. EI encourages us to deviate from the baseline values to match our lifestyle, being aware of the links in the metabolic chain, Light==>CO2==>Nutrients==>Waste==>WC

Cheers,


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