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Old 18-03-2003, 09:44 AM
Mark Trueman
 
Posts: n/a
Default Do i need magnesium??

Firstly some background

Im running a 160litre planted tank, pretty heavily planted. Pressurised co2
at about 25 ppm, 120 watts of lighting 10 hrs a day; 5hrs light, 2 dark, 5
light. Plants are growing ok but i think there is some problem with the take
up of some nutrients. Im dosing as recommended by numerous sources as
follows. Firstly, a rundown of my tapwater, im doing 50% water changes
weekly on a saturday.

Tap water
Iron 0.017ppm
Nitrate 40ppm
Alkalinity as HCO3 289ppm
Calcium 134ppm
Magnesium 3.8ppm (*LOW??*)
Potassium 4ppm
Treating tapwater with Hagen Aqua Plus for chloramines.

PH with co2 injection in my tank is about 7.2

Here is what i have been dosing....
20ppm potassium sulphate once a week with water change
0.5 ppm potassium phosphate twice a week, on a tuesday and thursday
No nitrate as yet, still high in my tank.
10ml Kent Freshwater Plant 2x a week on tuesday and thursday.

Ive been dosing this for 4 weeks now and plants have been growing well but
bba has started to appear on some of my slow growers. I bought a phosphate
and iron test kit today and my tank is currently in the following state (its
a monday night)

Nitrates 20ppm
Iron (chelated) .75ppm
Phosphates 1ppm.

I would have thought my phosphates would be lower and that this is probably
what is causing the BBA. Im going to stop dosing this until my phosphates
get a bit lower. This is my main priority; i want phosphates to be the
limiting nutrient in my tank. Currently it seems to be something else.

Ive also notices that some of my leaves are developing yellow edges and
brown veins which i initialy thought to be due to iron deficiency. Turns out
that this isnt the case (assuming a valid test kit) so i'm led to Magnesium
(or lack thereof) preventing the uptake of the iron.

QUESTIONS

Is it more than likely that magnesium is what im missing??

If so, what ppm of magnesium do i need to aim for?

IMAGES
Some images may help

What is the problem here - http://www.marktrueman.com/images/brownvein.jpg
The veins of this plant are brown?? Any ideas???

http://www.marktrueman.com/images/irondef.jpg
Is the yellow leaf iron/magnesium deficiency? (Excuse the black molly in the
photo)

And heres a recent pic of the tank if you are interested
http://www.marktrueman.com/images/tank.jpg

Thanks for your help

Mark







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Old 18-03-2003, 09:44 AM
Aqua
 
Posts: n/a
Default Do i need magnesium??

What is the problem here - http://www.marktrueman.com/images/brownvein.jpg
The veins of this plant are brown?? Any ideas???


I have exactly similar plant. New leaves generally like that. But it will
change to dark green within few days. BTW what is that plant?

--
Thank You

Dominic
http://www.dlink.org/aqua



  #3   Report Post  
Old 18-03-2003, 09:44 AM
Mark Trueman
 
Posts: n/a
Default Do i need magnesium??

I think its some kind of Echinodorus, not sure which one, maybe "tricolor"

No ideas on the magnesium then??

Mark

"Aqua" wrote in message
...
What is the problem here -

http://www.marktrueman.com/images/brownvein.jpg
The veins of this plant are brown?? Any ideas???


I have exactly similar plant. New leaves generally like that. But it will
change to dark green within few days. BTW what is that plant?

--
Thank You

Dominic
http://www.dlink.org/aqua





  #4   Report Post  
Old 18-03-2003, 10:56 PM
Alex R
 
Posts: n/a
Default Do i need magnesium??

"Mark Trueman" wrote in message
...
Firstly some background

Im running a 160litre planted tank, pretty heavily planted. Pressurised

co2
at about 25 ppm, 120 watts of lighting 10 hrs a day; 5hrs light, 2 dark, 5
light. Plants are growing ok but i think there is some problem with the

take
up of some nutrients. Im dosing as recommended by numerous sources as
follows. Firstly, a rundown of my tapwater, im doing 50% water changes
weekly on a saturday.


There is no need to have a dark period in your tank. It disrupts the natural
daily plant cycle and it doesn't help with algae.

Tap water
Iron 0.017ppm
Nitrate 40ppm
Alkalinity as HCO3 289ppm
Calcium 134ppm
Magnesium 3.8ppm (*LOW??*)


I would add some Mg in this case. It might never be depleted at this level,
but I believe it has to be balanced with the calcium, or the calcium might
block the consumption of Mg. I'd aim for 50 ppm Mg. MgSO4 is cheap and easy
to find. I have a lot of Ca but no measurable Mg in my tap water, and I add
about 2 degrees worth of Mg every week.

PH with co2 injection in my tank is about 7.2


According to my calculations, your KH as CaCO3 is 26 degrees, which would
give you 49 ppm CO2 with that pH. If that's correct, it's a little high.

Here is what i have been dosing....
20ppm potassium sulphate once a week with water change
0.5 ppm potassium phosphate twice a week, on a tuesday and thursday
No nitrate as yet, still high in my tank.
10ml Kent Freshwater Plant 2x a week on tuesday and thursday.


Nitrates 20ppm
Iron (chelated) .75ppm
Phosphates 1ppm.

I would have thought my phosphates would be lower and that this is

probably
what is causing the BBA. Im going to stop dosing this until my phosphates
get a bit lower. This is my main priority; i want phosphates to be the
limiting nutrient in my tank. Currently it seems to be something else.


The PO4 is not what's causing your BBA. Stopping the addition of PO4 will
just make it worse. You have to figure out what nutrients your plants are
lacking. Because you're not adding KNO3 (and that's okay), you should add
more K2SO4 to make up for the K in KNO3. I'm not sure if you meant that you
were adding 20 ppm of K2SO4 or 20 ppm of K from K2SO4, but I would dose at
least 25 ppm of K per week just to be on the safe side. It will be dangerous
to have the PO4 be the limiting nutrient in your high-light tank. The
nutrient that you want to be limiting is light.

It is likely that the poor health of some of your plants and the appearance
of BBA are connected. Address the deficiency symptoms and the algae will
retreat. From your photos, it looks like it could be one of a number of
trace deficiencies. Are those symptoms occuring on new leaves or old leaves?
If new leaves are affected, it usually suggests a lack of traces. Old leaves
suggests a lack of macros. I would increase the Kent supplement a little bit
and see if that helps. But I would add some MgSO4 first.
__
Alex
pcalex (at) hotpop.com


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Old 19-03-2003, 12:09 AM
Mark Trueman
 
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Default Do i need magnesium??

There is no need to have a dark period in your tank. It disrupts the
natural
daily plant cycle and it doesn't help with algae.


Funny you should say that, an hour before i even read your response i had
removed the dark period from my tank.

PH with co2 injection in my tank is about 7.2


According to my calculations, your KH as CaCO3 is 26 degrees, which would
give you 49 ppm CO2 with that pH. If that's correct, it's a little high.


I have conflicting readings, my water authority gives me that value of
289ppm (which i work out as 289/17.86=16.81dKH using the formulae on
http://www.thekrib.com/Plants/CO2/ha...arryfrank.html) but when i test
kh with a test kit from the tap it comes out at about 13 dKH which i believe
is about 22 ppm co2. Id rather go with a test kit of my own water. Im only
bubbling 40 bubbles a minute into my eheim so i cant see that i would be
able to get 49ppm with that, even if my kh was 26. Im probably one of many
who doesnt quite understand kh/gh. My kh test kit says 13 so thats what im
going with!!

Here is what i have been dosing....
20ppm potassium sulphate once a week with water change
0.5 ppm potassium phosphate twice a week, on a tuesday and thursday
No nitrate as yet, still high in my tank.
10ml Kent Freshwater Plant 2x a week on tuesday and thursday.


Nitrates 20ppm
Iron (chelated) .75ppm
Phosphates 1ppm.

I would have thought my phosphates would be lower and that this is

probably
what is causing the BBA. Im going to stop dosing this until my

phosphates
get a bit lower. This is my main priority; i want phosphates to be the
limiting nutrient in my tank. Currently it seems to be something else.


I'm not sure if you meant that you
were adding 20 ppm of K2SO4 or 20 ppm of K from K2SO4,


dosing enough k2so4 to put in 20ppm of K per week, i sometimes put a bit in
mid week as well.

Are those symptoms occuring on new leaves or old leaves?


Its old leaves, so you suggest a possible lack of macros. I think most of my
macros are in abundance, the only one i dont test is K and i add about 20ppm
per week of that.

You also say about increasing my trace mix dosage. Im worried about too much
iron, my current dosage has my iron at about 1ppm currently which i think is
a bit too high. Maybe this will decrease faster as i add mgso4; the
trace+iron will be taken up by the plants at a faster rate, keeping the iron
levels down.

How much Mgso4 do i need to get to the 50ppm you mentioned? Those
calculations throw me!! I think its about 14 tsp a week (using the krib
pages) in my tank of 160 litres, maybe you could confirm this. Seems like a
lot of mgs04.

Thanks for your help

Mark





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Old 19-03-2003, 01:32 AM
Alex R
 
Posts: n/a
Default Do i need magnesium??

"Mark Trueman" wrote in message
...
PH with co2 injection in my tank is about 7.2


According to my calculations, your KH as CaCO3 is 26 degrees, which

would
give you 49 ppm CO2 with that pH. If that's correct, it's a little high.


I have conflicting readings, my water authority gives me that value of
289ppm (which i work out as 289/17.86=16.81dKH using the formulae on
http://www.thekrib.com/Plants/CO2/ha...arryfrank.html) but when i

test
kh with a test kit from the tap it comes out at about 13 dKH which i

believe
is about 22 ppm co2. Id rather go with a test kit of my own water. Im only
bubbling 40 bubbles a minute into my eheim so i cant see that i would be
able to get 49ppm with that, even if my kh was 26. Im probably one of many
who doesnt quite understand kh/gh. My kh test kit says 13 so thats what im
going with!!


Yeah, I kind of suspected that might not be right because it's unusually
high. KH test kits measure alkalinity as CaCO3, not HCO3. The ratio of the
atomic weights of CaCO3 and HCO3 is about 1.6, so the alkalinity in the
published water analysis is really 473 ppm, or 26 degrees. But yes, I would
go with the results of the KH test kit, as you're doing.

Are those symptoms occuring on new leaves or old leaves?


Its old leaves, so you suggest a possible lack of macros. I think most of

my
macros are in abundance, the only one i dont test is K and i add about

20ppm
per week of that.


Well, in that case, Chuck Gadd's nutrient deficiency article at
http://www.csd.net/~cgadd/aqua/art_plant_nutrient.htm suggests it might be
the magnesium as well. That's one more sign that your plants are lacking Mg.

You also say about increasing my trace mix dosage. Im worried about too

much
iron, my current dosage has my iron at about 1ppm currently which i think

is
a bit too high. Maybe this will decrease faster as i add mgso4; the
trace+iron will be taken up by the plants at a faster rate, keeping the

iron
levels down.


The iron test kits are not really useful for determining how much iron is
available to plants and it's unclear what kind of iron they are measuring.
Other hobbyists keep Fe at 1.0 ppm without problems. I add about 0.7 ppm per
week to my high-light tank, and it never measures very high. But if you say
that it's the old leaves that are affected, try adding the Mg first before
increasing the traces. And keep up that PO4.

How much Mgso4 do i need to get to the 50ppm you mentioned? Those
calculations throw me!! I think its about 14 tsp a week (using the krib
pages) in my tank of 160 litres, maybe you could confirm this. Seems like

a
lot of mgs04.


The quick way is to just add the dry MgSO4 gradually until your measured GH
increases by 2 or 3 degrees. It's definitely not 14 tsp a week. For my
30-gal. tank, one mL (1/5 tsp) of dry MgSO4 by volume increases the GH by
one degree. You could also use Chuck's nutrient dosage calculator at
http://www.csd.net/~cgadd/aqua/art_p...osage_calc.htm to make an MgSO4
solution.
__
Alex
pcalex (at) hotpop.com


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Old 19-03-2003, 02:32 AM
Aqua
 
Posts: n/a
Default Do i need magnesium??

Magnesium 3.8ppm (*LOW??*)

How did you calculate this Mg Level?

--
Thank You

Dominic
http://www.dlink.org/aqua



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Old 19-03-2003, 09:56 AM
Mark Trueman
 
Posts: n/a
Default Do i need magnesium??

"Aqua" wrote in message ...
Magnesium 3.8ppm (*LOW??*)


How did you calculate this Mg Level?


Its what's on the report from my water people. I dont think you can
get test kits easily for Mg can you??
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Old 19-03-2003, 11:08 PM
Philippe Lemaire
 
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Default Do i need magnesium??

You can subtract Ca from GH (normally Ca+Mg)...

Philippe


"Mark Trueman" wrote in message om...
| "Aqua" wrote in message ...
| Magnesium 3.8ppm (*LOW??*)
|
| How did you calculate this Mg Level?
|
| Its what's on the report from my water people. I dont think you can
| get test kits easily for Mg can you??

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Old 20-03-2003, 03:20 AM
Aqua
 
Posts: n/a
Default Do i need magnesium??

You can subtract Ca from GH (normally Ca+Mg)...

Sorry guys, How do you measure Ca? Do you have any test kit for Ca?

--
Thank You

Dominic
http://www.dlink.org/aqua



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