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While I am not an expert nor do I have matter-of-fact links to back any of this up, I believe that a calcium:magnesium ion ratio of between 3:1 and 4:1 (ca:mg) is optimal. Personally I use RO/DI water and dose a 4:1 ratio based on molecular weights.

I think this is something that is often overlooked, I see a lot of people say "I use Epsom Salts to raise GH," well that is only going to increase magnesium and it will be WAY high of a ratio to calcium.
 

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Hi
I have done experiments with Ca and Mg levels and ratios. Generally plants don’t care about ratios as long as there are some levels present. Ca is immobile element and therefore must be present constantly.
Not the same can be said about mobile Mg. Mg can be dosed in very small quantities and still be sufficient. Additionally, higher levels of Mg harm some plant species, example is Rotala Wallichii.

Thank you
Edward
 

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Having some issues with Mg, or lack thereof, I too would like to know what kind of damage you're talking about Edward in respect to wallichi. How does it manifest itself? Have you seen it in other plants as well?
 

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What about issues of Mg blocking Ca. I switched from Flourish to CSM+B several months ago and since then I have had many issues I contributed to trace defficiency. In the end I was dosing 6ml, 3x week, of the standard CSM+b solution to a 15 gallon, high light tank. Macros were dosed 4x week with 10mg/l NO3 and 1.5-2 mg/l PO4. Eco/onyx substrate, high fish load and press CO2 in the 25+ range. I also have a 10, similar setup and dosing but I dose 4-5ml CSM+B 3x week.
All my tanks run a Gh of 9+ and generally a kH of 3+
Even with all that trace I was seeing deficiencies of leaf curling, tip stunting and necrosis on the stems with plants, including Rotala vietnam (similar to wallachi in apperance and growth patterns) H. micranthemoides, Ludwigia arcuata, Hedoytis sp Rio, Mayaca fluviatalis, P stellata narrow leaf and even sever curling and white spots on new growth of Anubias nana and petite. A question posted here to APC lead to a response (by Phil Edwards) that the high Mg levels in CSM might be causeing a Ca blockage/deficiency. Not having any other trace to use, nor a local source for Flourish (*my favorite) I tried a quick fix of dosing 1 drop per gallon/per day of Kent Concentrated Liquid calcium. With in 3-4 days i was noticing signs of improvment. I did not change any other parameters during this time. I cut the liquid calcium and started adding 1/4tsp of Seachem Equilibrium. I now occaionally see small signs of stunting in my anubias, P stellata and HM but only on the occasional stem, not 3/4 of the bunch like before. All my other fine leaved plants succumed and were lost by this time. I attrubute most of my trace issues now with the high Mg, Ca and K that have to be in my tank by now. I need to get away from the CSM i think;)

Also, for some reason I can't seem to keep Nerite snails for more than a few weeks. Could it be related to the hardness ions?

What are ya'lls thoughts on this?
 

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Well Dennis,
i am using seachem flourish and dose 40ml per week (10ml each time..4 times per week) on top of this i dose the same amount of seachem iron.. and my plants still turn out like this with all this trace I see the same thing as you.. mainly being leaf curling, tip stunting and necrosis on certain stemsplants like didipls diandra. My Rotala vietnam was particularly BAD..but my other plants were pretty okay..even though if you look closely..they dont look like they are at tip top condition..the best that they can be..
so i added a bag of corals into my filter and after about a week.. boom... the vietnam came back to life.. and the DD started growning at an insane rate. Problem is i left the bag too long in the filter and now my kh is like 12!! and the plants are dying. So 2 weeks ago i removed the bag of corals and have now done 2 waterchanges since then..the plants are reverting back to their old self...and this really irritates me.. the tip of my ludwigia pantanal have colour but are small and scrony leaves.. so now maybe i'll go find some liquid calcium like you to dose..and see waht happens.. i will not change anything in the fert regime during this time..
 

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Dennis, I am curious if you have ever determined how much of your gh is from Ca vs Mg? In my case I have a gh of 11, and kept seeing curling stunting on and off on my A. reinickii. So I bought a Ca test kit and found most of my gh came from Ca. I started adding Mg and saw improvements, with still the ocasional stunting. I got some aromatica recently and am having a heck of a time with it - growing real slowly, older leaves getting pinholes and stems rotting. So I am in the process of gradually increasing the Mg to see if it helps. Do you know at what point (Ca/Mg ratio) is it you see inhibition?
 

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Bert, in short, I don't know the answers to any of your questions. I can't find a Ca test locally that will work for freshwater so I have no idea of my hardness ratio. I don't think it is Mg deficieny as I though Mg would show up on older leaves. My issues all happen to new growth. Also, I know that my original fertalizing (with the CSM) added plenty of Mg but no Ca to speak of, hence my reasoning behind the Mg excess/Ca deficency. Adding Ca seems to have cleared up 90% of the problem. I have some Flourish on the way and will see how things look after using that for 2-3 weeks. I do notice the Gurus recommend Flourish or TMG but not CSM.
 

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I am relatively new at this chemistry thing but I have an interest in this Ca/Mg relationship. According to my calculations, I need to be adding about 2.5 teaspoons of Epson salts to my 30 gallon tank each water change to get a 4:1 relationship of Ca to Mg.

Hopefully, my calculations are screwed up as that seems to be alot. Anyway, here's how I came to that conclusion. According to my city water company, I have 40 ppm of Ca in my tap water and my GH tests at 100ppm with 2 different testing kits. I downloaded a MgGH calculator program by Stuart Keeler and after plugging in that bit of info, it calculates I have 0 Mg in my tap water (which I believe according to the symptoms my plants are showing - old leaves have yellow/brown spots which develop to pinholes). According to the fertilator, I need to add 2.5 tsp of Epson salts to get about 10ppm of Mg to meet the 4:1 ratio.

I guess I have 2 questions. Is that correct, that I need to add that much? And if so, should I do it all at once or break it up over multiple days?

I am dosing EI, pressurized CO2 at 40ppm (KH of 4, Ph of 6.5), 4.5WPG for 6 Hours, 2.5WPG for 4 hours (2 lights, 2 timers), medium fish load, medium to heavily planted with Bacopa C., Rotala Rotundafolia, Hygrophila Difformis, E. Tenellus, Ludwigia Repens, Java Fern, Altenethera Reneicki.

Thanks,

Mike Herod
 

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Bert H said:
Dennis, I am curious if you have ever determined how much of your gh is from Ca vs Mg? In my case I have a gh of 11, and kept seeing curling stunting on and off on my A. reinickii. So I bought a Ca test kit and found most of my gh came from Ca. I started adding Mg and saw improvements, with still the ocasional stunting. I got some aromatica recently and am having a heck of a time with it - growing real slowly, older leaves getting pinholes and stems rotting. So I am in the process of gradually increasing the Mg to see if it helps. Do you know at what point (Ca/Mg ratio) is it you see inhibition?
Well I was finally to check my waer chemistry today. TDS from Hanna meter and Ca levels from Salifert test

Tank: Tap:
TDS 264 ppm TDS 96ppm
GH 12*= 213.6ppm GH 8*=142.4
Ca 150ppm Ca 120ppm
Mg 63ppm Mg 22ppm

That means that my tapwater has pretty good parameters but my tank water is out of wack due to, I assume, my heavy dosing of CSM and the use of and Onyx/Eco mixed substrate.

Also, can the tap measurments be correct? Is it possible to have a Gh higher than your TDS?
 

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dennis said:
Well I was finally to check my waer chemistry today. TDS from Hanna meter and Ca levels from Salifert test

Tank: Tap:
TDS 264 ppm TDS 96ppm
GH 12*= 213.6ppm GH 8*=142.4
Ca 150ppm Ca 120ppm
Mg 63ppm Mg 22ppm

That means that my tapwater has pretty good parameters but my tank water is out of wack due to, I assume, my heavy dosing of CSM and the use of and Onyx/Eco mixed substrate.

Also, can the tap measurments be correct? Is it possible to have a Gh higher than your TDS?
Your Ca and Mg numbers are stilll in CaCO3 equivalent numbers, the real ppm for Ca and Mg are:

Ca 60ppm 48ppm (divide your numbers by 2.5)
Mg 15ppm 5 ppm (divide your numbers by 4.1)

I guess it is possible for TDS and GH to mismatch to some degree. There are assumptions built into each that neither truely reflects the real ppm in your water. TDS measures electrical charges and assume that they are from a given composition of ions(depending on factory calibration fluid used, for example, NaCl, KCl, or some other salt mixture) and convert it into ppm. On the other hand. GH measures the total multivalent ions(mostly Ca++ and Mg++ typically) and assume that they are all from CaCO3 and converts it into CaCO3 ppm in most test kits. Still, it is a bit odd your tap TDS is so much lower. I did a simple calculation, assuming you only have GH ions in water and your TDS uses NaCl, it should actually give slightly higher reading than GH. Due to the electrical charge differences, TDS meter should see two NaCl molecules(molecular weight 56) for every CaCO3(molecular weight 100) molecule seen by the GH kit, unless this assumption of mine is wrong and they see it one for one.
 

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So, in my tank I have 60:15 Ca:Mg, or 4:1. That is perfect now. Guess maybe that is why my stunting is 90% gone. this change probably happened in th elast 2 weeks since switching to Flourish and doing a few wc's with water that has a 9.6:1 ratio. That has probably helped balance things out a bit.

Now there is only one problem. Silly me, I just went and dosed 35ppm Ca. I added 20 ml of Kent's Liquid Calcium. I figured I needed 100ppm of Ca, based on my previous post of 150ppm Ca and 63ppm Mg, to bring my ratio up to the correct amount. I figured adding about 1/3 this week would be a good start in the right direction.

Nuts! Think that will hurt anything?

Oh, and BTW....in my 12 degree hard water, I am growing Rotala sp, formerly known as Ammania Bonsai, Downoi, P. stellata and Ludwidia Cuba with beautiful success. The plants I was having stunting issues with before were P stellata, Anubias nana, H. micranthemoides and Mayaca fluvitalis.

guess I won't have calcium issues for a few weeks huh;)
 

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Keep in mind that our tests have limited resolution and your tap water only has 5ppm Mg, so it could have been less. I bet the problem was TOO LITTLE Mg in the beginning. Now that you have about 15ppm Mg, things look better. I had similar stunting issues, adding Mg via epsom salt helped a lot.
 

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I would be inclined to agree with your Shalu except for 2 things. First, I don't know what my parameters were a month or 2 ago whe this issue was real bad, but I do know I was dosing heavily with CSM+B, a product that contains lots of Mg but almost no Ca. I was not adding Ca or Mg from any other source except water changes. Secondly, the issue I had with m y plants was easy to see in the Anubias leaves. New growth only was affected and the problems were litght spots, curling and holes in the leaves. Mg is a mobile nutrient, meaning that plants will take it from old growth to feed new growth when there is a deficiency No plants in my tanks exhibited issues with old growth.
 

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I know people say Mg affects mostly old growth, but my problem was mainly with new growth, and adding epsom salt definately helped a lot, especially with alternanthera reneckii stunting problem. I think mg in CSM will hardly make any dent in terms of ppm, did you estimate how much it was really adding in terms of ppm in the tank? Ok, I did a rough estimate, typically it will be 1ppm per week of dosage, 2ppm Mg per week from very heavy dose of CSM.
 

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Mg is more common for issues, many suggested it was K+, but CO2 and Mg will influence that more than Ca which tends to rarely an issue but an oft loved excuse for poor growth.

High levels of NH4+ and Mg++ will block K+ far more than K+ ever will.
And there is research to support that.

So do not go nuts with Mg.
You just need a little bit and the ratio itself is not going to cause much issue if the Ca is high. 10-20ppm is more than enough.

Regards,
Tom Barr
 
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