# Problems with doing a 50% water change if I use EI.



## maj74 (31 Oct 2008)

I would like to try using the EI method now my tank is planted up. The problem is this. I use rainwater in my tanks, and have done for several years, having almost no problems with fish compared with those when I used tapwater. The Discus especially benefit as we have very hard water in our area.

My problem is this. With a 250l tank, a 50% water change is not surprisingly 125l and especially in winter, there's no way I can change this much water in one go, as it needs to be stored in the house to warm up. (I don't fancy putting water close to freezing in a planted discus tank!)

Can the EI method be used if following a method such as 50 litres being changed twice a week? (or even better, 25 litres every two days, though I suspect this is not enough)

If I carry out water smaller water changes every couple of days, how could the dosing regime work? Is it at all possible?

Any info gratefully recieved!!


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## B4M (31 Oct 2008)

Hi,

Why not buy a cheap kettle and boil the rain water? Even in winter you'd only need about 25% boiled to heat a bucket of cold. 
You may have more of an issue in summer due to lack of rain but that won't change whether 10% every 2 days or 50% every 10. 

Just a thought,  

B4M


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## steve2tanks (1 Nov 2008)

Could you not stick a heater in to heat the water up?

Thats what i do for my 240lt tank that i do a 50% water change on every week :?:


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## ceg4048 (1 Nov 2008)

Hi,
    The focus should be on keeping the tank clean and to minimize organic waste. The same philosophy that Discus keepers employ to maintain cleanliness is consistent with EI. The higher the light and the more CO2 that is injected the more growth and organic waste is produced. It is not necessary to get hung up on some magic number like 50% or whatever. Give more thought to the principles of plant growth that you are trying to execute and this will enable you to make the proper adjustments. So if you avoid mega-wattage lighting levels this requires much less CO2 and consequently lower nutrient levels. Less waste=>Lower volume of water changes.

Cheers,


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## Themuleous (1 Nov 2008)

This is exactly the problem Im looking at with my 4ft, which I'm using rainwater on.  Would be interested to see what solution you get.  At the moment I'm using 60lt very cold rainwater with 40lt hot tap water both added directly to the tank.  That seems to level the temperate out when I do a water change.

Sam


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## maj74 (1 Nov 2008)

ceg4048 said:
			
		

> Hi,
> The focus should be on keeping the tank clean and to minimize organic waste. The same philosophy that Discus keepers employ to maintain cleanliness is consistent with EI. The higher the light and the more CO2 that is injected the more growth and organic waste is produced. It is not necessary to get hung up on some magic number like 50% or whatever. Give more thought to the principles of plant growth that you are trying to execute and this will enable you to make the proper adjustments. So if you avoid mega-wattage lighting levels this requires much less CO2 and consequently lower nutrient levels. Less waste=>Lower volume of water changes.
> 
> Cheers,



Thanks for the reply, and I'm glad that the 50% figure is not something that has to be fixed. If I did work on a set amount being changed every couple of days, then how would the EI dosing regime be organised?


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## Behold (1 Nov 2008)

sorry slightly of topic..... EI???? what is that?


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## milla (1 Nov 2008)

Behold said:
			
		

> sorry slightly of topic..... EI???? what is that?



read this viewtopic.php?f=34&t=1211


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## ceg4048 (1 Nov 2008)

maj74 said:
			
		

> Thanks for the reply, and I'm glad that the 50% figure is not something that has to be fixed. If I did work on a set amount being changed every couple of days, then how would the EI dosing regime be organised?



Well, in the baseline dosing scheme one would typically dose the normal amount immediately following the 50% water change. So for the 250L tank that would mean 3/4 teaspoon KNO3 for example. Now, there is nothing wrong with just using that value each time even if you were doing say, two 25% changes per week in lieu of a single 50% change. I mean, the dry salts are certainly cheap enough and it makes life so easy because you just reset the dosing each time you do a water change without having to be a mathematician. But instead of dosing 3/4 teaspoon you could just halve the dose on each of the two 25% changes so that instead of doing a full reset once a week you can do a "half-a-reset" i.e. 3/8 teaspoon KNO3 twice a week (assuming you are doing two 25% water changes per week.)

Again, Moses did not come down from Mount Sinai to hand me this idea carved on a stone tablet. We're just trying to ensure that we don't fall below the standard concentration levels of the nutrients. Resetting the full dosage amounts does no harm, is easy, but is wasteful and drives high growth rates, meaning more maintenance. Fractional resets are more logical and more frugal but is also more complicated, especially if you are using prepared solutions instead of just dosing dry. So try one way, see how it goes for three weeks or so and then try the other way and compare the tradeoff of ease/growth versus cost.

Hope this makes sense...

Cheers,


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## John Starkey (2 Nov 2008)

Themuleous said:
			
		

> This is exactly the problem Im looking at with my 4ft, which I'm using rainwater on.  Would be interested to see what solution you get.  At the moment I'm using 60lt very cold rainwater with 40lt hot tap water both added directly to the tank.  That seems to level the temperate out when I do a water change.
> 
> Sam


Hi Sam,just a word of warning Sam,you should not add hot water to your tank straight from the tap because it contains total disolved solids (tds)and this would be harmful to your fish,regards john.
I change 50g each week and at this time of year i just add boiled water to the tank along with what goes in from the garden hose,the one thing i do differently at this time of year is refill the tank a lot slower,i also add my seachem prime straight to the tank and i have never lost any fish in well over a year, regards john.


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## JamesM (2 Nov 2008)

I've been adding hot water straight from the tap for years with no ill effects to fish or shrimp.


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## B4M (2 Nov 2008)

john starkey said:
			
		

> Hi Sam,just a word of warning Sam,you should not add hot water to your tank straight from the tap because it contains total dissolved solids (tds)and this would be harmful to your fish,regards john.



I thought this was the case too but sufficient people on here stated they used hot from the tap so I gave it a go. A couple of months in and no adverse effects. It's much easier and quicker so I'll be sticking to the tap unless the fish tell me otherwise.

Going back to the original point of frequent water changes rather than 50% per week. If you do 50% per week then after 1 week you have 50% original water, after two weeks you will have 25% original water, and after 3 weeks 12.5% original water. If you do 10% every 2 days you will have 90% original water, then 81% original after the second change and after 10 changes (20 days) you will still have 35% of you original water in the tank. So after 3 weeks changing 50% a week you have 12.5% of the original water compared to 35% if changing 10% every two days. i.e. with frequent small changes you are removing some of the water you only added a few days ago. 
That's not to say it won't work just it's less efficient than larger weekly changes. 

B4M


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## plantbrain (3 Nov 2008)

I adjust the temp from the tap in my bath shower head to get the right temp(your hand can tell differences to within 1 Degree C), add water and add dechlorinator straight.

I have Cardinals, Altums, CRS etc, all the so called sensitive species.
Those TDS's are plant nutrients


Regards, 
Tom Barr


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## SteveyG (4 Nov 2008)

john starkey said:
			
		

> Hi Sam,just a word of warning Sam,you should not add hot water to your tank straight from the tap because it contains total disolved solids (tds)and this would be harmful to your fish,regards john.



There should be no problem filling from the tap if you have a combi boiler.


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