# Do I need magnesium Sulfate (MgSO4)?



## mede

Starting up a new tank which will be planted and filled with water this weekend. I'm dosing EI and I was wondering if I need magnesium Sulfate (MgSO4) (is this the correct English translation??)

How to decide if I need to dose MgSO4 beside my KNO3, KH2PO4 and CSM+B?

It's still not clear to me what's the advantage/disadvantage is.....


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## ceg4048

Hello,
		 I'm not familiar with the origin of the water supply in Holland, and there would be no hope my trying to read a Dutch water report, but sometimes the municipal water report on-line will contain information about Magnesium and Calcium levels in the tap.

In any case, it doesn't really matter if you can find that information or not. It's always a good policy to start by adding a few teaspoons of MgSO4 (or even MgNO3) at water change time and then slowly reduce the amount to see if there is a difference.

Magnesium is discussed in greater detail in About Magnesium | UK Aquatic Plant Society

Cheers,


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## mede

Thanks Ceg! (Reading the link about Magnesium right now.... )

Just checked the water report for my home address, and see the following values for Magnesium and Calcium:

magnesium	mg/l Mg	7,81
calcium		mg/l Ca	44,9

I'm mixing my tapwater with osmose water because the tapwater is average hard.

The water report is calling it (translated) total hardness:

o D	8,1

And the hardness (is this the same??) is noted as:

8.1°D (1mMol = 5,6° D)

No idea if these values are OK, or if it's even better to leave the osmose water and just use my tapwater? I always try to keep a KH value of 4 (so mixing 50% tap water with 50% osmose)


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## ceg4048

Hello,
		  Again, you really should not care about what the hardness is. I can think of about 5 species of plants that actually care. If you are cutting your tap water with osmosis water for your fish then that is a different issue, but if you are doing it for your plants, and if you don't have any of those sensitive plant species then you are wasting your time and energy.

The Mg value given in your report looks like a good number and so you probably don't need to add any Magnesium, however, as I mentioned, it's always a good idea to at least try the addition to see if there is a difference.

Water reports do not provide data for your particular house. It would be impractical to measure the parameters for all houses. What they do is to take measurements in several zones and then apply those measure values to the homes within that zone.

Cheers,


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## mede

Thanks again!

So it won't be a problem to use 100% tap water? I always thought that the co2 uptake for plants is better with low KH values. My tap water has a KH value of 8, that's why I'm mixing it to get KH 4.

If this really doesn't matter then it will save me a lot of time!


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## ceg4048

Here is a tank with 100% tap water. The water had 15 dKH and 21+ GH.
Just to be obnoxious, I added another 5GH using GH Booster, so the total was 15KH and 26+ GH. If your plants have trouble uptaking CO2, it will be because of something that you are doing or not doing, not because of tap water with KH 8.





Cheers,


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## mede

well, that's an amazing tank!

This morning filled my tank with water and plant with just tapwater (KH 8) and created macro/micro fertilizers with a few teaspoons MgSO4.
Hopefully my tank will look like  this one in a few months 

Maybe not the right topic to ask; is it better to do 50% water changes every day the first week, then every seconds day the second week and so on until you can do 50% water change once a week?


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## ceg4048

Hi,
	Save yourself from possible strain and injury and just do the water change 2X or 3X per week. If possible, do the water change just before lights on. You can change more than 50% of course. The more, the better. The 50% is just a guideline, not a hard value. Sometimes you can do less frequent or less volume change, but you'd normally have to make some other concession, like using less light so that you can use less CO2 and less nutrients. Plants really LOVE clean water. I can't emphasize this enough. It's the single most important thing you can do.

Cheers,


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## sa80mark

Sorry to highjack your thread mede,

Ceg you said to do the water change just before lights on, is there a reason for this ? I was doing mine at lights out as I probably wrongly presumed that doing it before lights on would mess my with my co2 levels ?

Thanks
Mark


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## ceg4048

OK, here's the deal:

These aquatic plants expend a lot of energy trying to maximize CO2 availability. That's a very tough proposition under water because the gas is not as easy to come by as it is in air (even when you are adding it).

In the morning, at lights on, they have a really difficult time getting their machinery running. Imagine they are a Ferrari on the track. They need time to warm up. Just because you switch the light on it doesn't mean that plants can switch everything on and operate at peak efficiency in an instant. Only algae can do anything close that.

When you drop the water level the plant leaves are exposed to air. They dry out, of course, if they are exposed for too long, but the duration of the water change is enough time to get the leaf saturated with air.....air that contains CO2 in bucketloads. So the plants are taking a massive gulp of CO2 when they are exposed. This is yet another reason I do as large a volume change as the fish can tolerate without becoming grounded in the sediment. The lower the water level, the more mass of leaves are exposed to air.

Then, when you fill the tank and turn the lights on they have gotten a head start because the CO2 is already exactly where it needs to be. Sugar production can begin very quickly. Combined with clean water, the process which removes the dirt and silt from the surface of the leaves, they get an even better head start.

Additionally, if you are using tap water, many municipalities have water which is exposed to CO2, either added intentionally, or absorbed while the water is in the aquifer or as it passes through CO2 containing sources on it's way to the aquifer. The water delivered under pressure to the tap often retains a high CO2 content. So then when the lights go on the Ferrari has a much better chance to make a clean getaway. It's like having all the stars line up.

You can get an idea of how much CO2 your tap water has by measuring the pH as it exits the tap and then measuring it after a few hours of sitting in a cup. If the pH rises significantly then this indicates that CO2 was in the water and evaporated, lowering the acidity thereby raising the pH.

If you have a non-CO2 enriched tank, then you have to worry about such large water changes near the photoperiod, and yes, a lights off water change can help avoid BBA (or just doing small water changes like 10%), but if you are dosing Excel and/or adding gas then this is the best time.

Cheers,


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## sa80mark

Thats great 
Thanks for the explanation,  makes perfect sense 

Mark


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## terry82517

Clive are u saying that there is more co2 in the tank directly after a water change then there is after 2 or 3 hours of injected co2, and that's y it's better to do it just before lights on?


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## ceg4048

No I'm not saying that at all. I'm saying that fresh water from the tap has more CO2 than fresh water left to sit on the kitchen counter for a few hours. The amount of CO2 that is added to the tank due to the fresh water imported into the tank is a bonus, just like on those television game shows.

Cheers,


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## mede

Interesting information! Unfortunately I'm only able to do water changes after light go off...

@Ceg: I assume that the 3x water changes per week is only meant for the first (or first two) week? After this I can use the weekly water changes according the EI-schema?

What about fertilization during the more frequent water changes? Isn't it true that I remove all macro/micro fertilization when doing more then one weekly water change? Now my EI-scheme is based on macro/micro dosing starting at Sunday and ending at Thursday.


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## ceg4048

mede said:


> @Ceg: I assume that the 3x water changes per week is only meant for the first (or first two) week? After this I can use the weekly water changes according the EI-schema?


My standard procedure is to use this frequency for the first 6-8 weeks of tank life. It takes that long for the tank to mature. However, if it is a burden then reduce the frequency and monitor the tank closely.




mede said:


> What about fertilization during the more frequent water changes? Isn't it true that I remove all macro/micro fertilization when doing more then one weekly water change? Now my EI-scheme is based on macro/micro dosing starting at Sunday and ending at Thursday.


Yes this is correct. Each time you do a water change therefore, you have transported the tank into a time warp to the next Sunday. So, begin the dosing cycle anew whenever you do the water change. Don't forget to wipe the slime/detritus off the leaves while you siphon the gunk away!




Cheers,


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## terry82517

Ok but wouldn't it be a waste injecting for 2/3 hours and then doing a water change? Would you not just lose lots of the co2 you spent 3 hours injecting down the drain? Or does putting the water back in introduce more co2 than you had originally, ie before water change but after 3 hours of injection? Sorry, just trying to get my head around it


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## ceg4048

Yes, that's true, if your CO2 comes on 2-3 hours before lights on, then you would be throwing a lot of that out the window. If your CO2 starts only an hour before lights on then this is less of a problem. How much you lose also depends on how your flow/distribution is.There is still a high level of CO2 in the tap water though, and remember, as I mentioned, the exposure to the air means that there is plenty of CO2. It's really not that much of a hit, everything considered, especially if you clean the leaves.

Cheers,


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## Reuben

This has piqued my interest!  Clive, how long before lights on does your Co2 come on?  I suppose if you are doing this water change system regularly you need not bother injecting Co2 before lights on?

I do an 80% water change every two days but do it 7hrs before lights on, when I refill I dose NPK.  The next day I dose traces, then the next day the cycle starts over...
My Co2 comes on 4hrs before lights on at the moment.  Is exposing the plants to the air before lights on much better than injecting Co2 to be at 'peak level' at lights onif the water is just as clean?


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## ceg4048

Well, 4 hours of pre-light CO2 is a long time. It ought not to need that much time to saturate the water. If it does, then there is something wrong with flow/distribution or with injection rate or dissolution method. Depending on the tank, 1 to 2 hours prior should be the sufficient.

I don't think there is any value in deleting the pre-light CO2 injection just because of the water change. Once the water change is complete, the gas needs to be turned on, pronto, because the light's coming on soon. The idea is to boost the CO2 levels with air and fresh water, and to reduce the obstacles to gas exchange on the outer leaf membrane by scrubbing it clean. If you boost the CO2 inside the plant, then it doesn't take that long for the amount of CO2 being injected to increase, and any delay in getting the levels up are mitigated by the fact that the plant has taken that gulp of air. This is not meant to replace the gas injection methods.

The water has to be changed at some point. That best point, i.e, the point which contributes most to plant health is just prior to the lights coming on. At other times, any advantage might be lost. This idea won't ever make or break your tank, so it's not some hidden secret weapon. All the things you do to your tank have a cumulative effect. The idea is to stack as many good effects together to maximize the chances of success.

When tanks suffer poor CO2, much of the time, the fault occurs during the first half of the photoperiod. Many complain that their DC is yellow late into the photoperiod, their fish sometimes are gasping, yet the plants melt or there is CO2 related algae. So it's the front end that needs to be fixed normally because the beginning of the photoperiod is the most important. Doing the water change at this time helps your injection methods, does not compete with the injection.

This is one of the reasons that people often report that their plants pearl just after a water change, but do not pearl on subsequent days at the same time when there is no water change. So if you have marginal to poor CO2 technique this is one of the indicators.

Cheers,


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## mede

Based on the discussion in this topic I want to follow the dosing scheme below:

Sun: Macro + water change (EI reset)
Mon: Micro
Tue: Macro
Wed: Micro + water change (EI reset) - after lights go off
Thu: Macro
Fri: Micro
Sat: Macro + water change (EI reset)

I'm only wondering if it matters that on week days I add fertilizers and do the water a change after the lights go off. During the weekend days I can do before light go on.

Maybe it's better to add on Wednesday micro before lights go on and dose a second time after the water change when lights go off? The point is that I can't manage to do a water change on week days before lights go on..... 

And a second doubt; is it better to start with macro dosing after water changes, or doesn't it matter (like my scheme above)?


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## GillesF

ceg4048 said:


> Hello,
> Again, you really should not care about what the hardness is. I can think of about 5 species of plants that actually care. If you are cutting your tap water with osmosis water for your fish then that is a different issue, but if you are doing it for your plants, and if you don't have any of those sensitive plant species then you are wasting your time and energy.
> 
> The Mg value given in your report looks like a good number and so you probably don't need to add any Magnesium, however, as I mentioned, it's always a good idea to at least try the addition to see if there is a difference.
> 
> Water reports do not provide data for your particular house. It would be impractical to measure the parameters for all houses. What they do is to take measurements in several zones and then apply those measure values to the homes within that zone.
> 
> Cheers,


 

Hey Clive

Is there any reason why it is believed that the low KH will improve CO2 absorption by the plants? And to what extent is this true?

Cheers,
Gilles


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## ceg4048

Hi Gilles,
Yes, there is a reason whose the origin is a fundamental optical illusion which is based on a very real chemical phenomenon.

The phenomenon is seen every time someone talks about the pH/KH/CO2 table.
The table appears typically as this:





The data in the table is derived from a series of equilibrium equations which begin with the basic form, something like this:
CO2 + H2O <=> H2CO3

This first equation states that when CO2 is added to water, the result is the formation of Carbonic acid (H2CO3).

Unfortunately, the fundamental flaw in reasoning occurs because everyone assumes that all the CO2 that you add immediately becomes Carbonic acid, and that as a result, in low KH water there is more CO2 because the pH is typically driven lower. These people also mistakenly assume that if you alter the KH, then that automatically means that you then also alter the CO2.

What is very much misunderstood, first of all, is that when you add CO2 to water, only a very tiny fraction of the gas enters into this equation. Depending on temperature, less than about 0.2% of the dissolved gas enters this Carbonic acid phase. This is explained more fully in the thread Stupidly used oyster shell gravel... | UK Aquatic Plant Society

Apart from all that, there is a fundamental misunderstanding of the difference between KH and Alkalinity.

So there may actually be a physiological effect on CO2 uptake performance due to Carbonate/Bicarbonate concentration levels, BUT KH test kits do not measure Carbonate/Bicarbonate content. So we really have no way of knowing. Just knowing the KH tells you nothing about how much Carbonate is in the water. Some plants may in fact respond negatively to the presence of the CO3 ion...maybe.....but the CO3 content of the water has little to no impact on the availability of dissolved CO2. This is a really important point..availability versus physiological response.

Having said that, of course, if you can see the limescale deposits caused by your tap water then that pretty much tells you that there is significant CaCO3, and water that is high in GH also typically is high in Carbonate content because, as I mentioned, the agent involved in driving the GH is usually Calcium Carbonate.

In any case, as you can see, there are many levels to this illusion. One has to do a deep dive to find the kernel of truth in order to avoid the hysteria surrounding the myths.

Cheers,


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## ceg4048

mede said:


> Based on the discussion in this topic I want to follow the dosing scheme below:
> 
> Sun: Macro + water change (EI reset)
> Mon: Micro
> Tue: Macro
> Wed: Micro + water change (EI reset) - after lights go off
> Thu: Macro
> Fri: Micro
> Sat: Macro + water change (EI reset)
> 
> I'm only wondering if it matters that on week days I add fertilizers and do the water a change after the lights go off. During the weekend days I can do before light go on.
> 
> Maybe it's better to add on Wednesday micro before lights go on and dose a second time after the water change when lights go off? The point is that I can't manage to do a water change on week days before lights go on.....
> 
> And a second doubt; is it better to start with macro dosing after water changes, or doesn't it matter (like my scheme above)?


 
Hi mate,
As I mentioned, it's really not a big problem. If you can't do the water change at a certain time, well, that's just how life goes. I really wouldn't worry about it. The most important thing is that you are changing the water. That is 1000X more important than the question of "when".

The same goes for adding the nutrients. It really doesn't matter what time of day. Obviously it does not make sense to add any nutrients just before a water change, right? Because that would just be throwing it away, but apart from that, there is no issue with what time, night or day.

Cheers,


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## GillesF

Thanks for the info!


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