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When to dose Mg and Ca

5447 Views 14 Replies 7 Participants Last post by  LadyHawk
Hello everyone! I've been lurking on the boards for quite awhile now and just recently became a member. I have a planted 60 gal and have just devised an EI dosing schedule for my ferts. After reading a bunch of posts about Mg and Ca, I'm still wondering: do you dose Mg and Ca with your Micronutrient doses or your Macronutrients? Or do most of you just dose on your WC day? It seems there has been plenty of discussion about this! I have relatively hard water, so I don't need to dose much of either, but I haven't been able to find a definitive answer. Thoughts? Thanks :)
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Hi LadyHawk,

Welcome to TPT!

I suggest getting a KH/GH test kit (make sure it does not have an expired date); I use the API KH/GH test kit. I don't worry to much about dKH except since I do use CO2 I like to keep the dKH at 3.0 degrees or slightly higher to avoid PH crash. I have very soft water (dGH = 1.0-2.0) so I have to add GH Booster (like Seachem Equilibrium). Several years ago when Tom Barr visited Seattle he suggested targeting about 4.0 dGH so that is what I do. You may have a dGH that is higher than 4.0, does that mean that your water has sufficient Ca and Mg for healthy plant grow? Unfortunately no, you may have lots of Ca (not uncommon in the Midwest where I grew up) but be deficient in Mg. Therefore I usually recommend dosing sufficient GH Booster to raise the dGH about two (2.0) degrees above the tap water hardness. Seachem Equilibrium has a handy dosing calculator to make it easy to dose. Hope this helps!
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That's great information, Seattle! Thanks for the quick response! I do have the KH/GH kit - My KH is usually 6/7 degrees (with a little baking soda - 2 tsps) and my GH is 11 (we have very hard water where I live :) I was thinking about getting a calcium testing kit to determine how much contributes to the hard water: I suspect I will need to add Mg to keep the proportions correct as, like you said, we probably have plenty of Ca but not Mg. I do add a little baking soda to raise the KH and the fish don't seem to care at all. It does help with CO2 ph swings (I have a full CO2 system set up) and I'll probably add a little for each water change. Would you recommend I get the Ca kit? Also, if I do need to add the Mg, which day should I dose on?
Hi LadyHawk,

Since CSM+B contains some magnesium (Mg) already I dose my magnesium and calcium (also iron (Fe)) the same day as my micronutrients. I tried to find the water analysis for Minneapolis to check your local Ca and Mg levels but could not find it on the municipal website; just that your water comes from the Mississippi. I am surprised that you KH and GH leves are that high if the water source is the Mississippi which is basically surface runoff water (btw I've been to the headwaters of the Mississippi). Are you by and chance outside of Minneapolis and your municipality is using well water?
Hello LadyHawk

I think you have hard water and with the caveat Seattle_Aquarist mentioned, you do not need to add major amounts of Ca , Mg or CO3. I found certain species did better when I increased my GH from 4 to 6 (like Hygrophila, Sagittaria and Myriophyllum) but take them as random observation not as establishing cause - effect.

To answer the question about timing...

a) dose at water change -target a major increase to match the previous/ideal aquarium water. Most people dose at this point if they have very soft water or use Reverse Osmosis (RO) water (KH~0 GH~0) (not your case)
b) with micros : Mg is part of many commercial solutions of micro nutrients. (JBL Fe+trace elements adds 3.3ppm Mg for every 0.13ppm Fe )
c) daily or with macros : as part of EI, the GH Booster was invented for people with very low GH. Plants use some amounts of Mg and Ca, especially if they grow fast and the GH Booster sol. targets a small addition of Mg Ca and K to be dosed regularly. There is no one formal description of ppm for this solution, various nutrient outlets offer their own mix. The description from nilocg website says Magnesium Sulfate, Potassium Sulfate, Calcium Sulfate(1:3:3 ratio)...whatever that means molar, mass or volume ratio ?. GLA Ultimate GH Booster has a nicer mix imho at 3,2ppmK , 1,66ppm Ca and 0,23ppm Mg
d) when /if needed. In waters with moderate to high GH, Ca is abundant enough. Mg might be missing but is easily spotted as white patches in old leaves while veins are still green. That and the fact that I have stopped seeing any deficiencies at 3ppm Mg.

As you can see you have plenty of playing room with these two nutrients. In aquariums for which I use RO water I target a KH of 4, GH 6. I find this is enough to not have to bother with the GH Booster even for a high light tank.

Hope this helped.

Regards
Duky
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Wow - this is all fantastic information!! Thank you so much! I'll keep an eye out for any deficiencies and adjust accordingly!

Also Seattle - the headwaters are beautiful! All I could find about the specific water we have here is that we purchase it from Minneapolis - and they have no water info on their site! I may try calling the public works to see if I can get some info through them.
I stopped worrying about how to add Ca to my tank when I finally located the report of my town's water source and realized how much Ca is already in there. However the Mg levels seem to fluctuate depending on which month they tested in... so I add Mg occasionally, when the plants seem to show symptoms. I use epsom salt, very little- less than half of a 1/32 teaspoon for dosing 35 gal, and literally 5 or 6 grains of the salt for dosing my 10gal. I dissolve it well in the tank water and dose along w/my other dry ferts.

Only once a month, lately I've been doing it once every 5 or 6 weeks. Probably not a perfect method but results are better now for me...
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Your water supplier is likely to be more than a handful of homes so it will be required to have the report available but it may not be online. The regs require different levels /size of suppliers to do different things to supply the info. Small companies don't have to maintain a website so be aware, it may be posted on a chalk board, in the office to read, etc, depending on the size of your supplier.
With hard water in the middle of the country, you are likely to have plenty of calcium so I find the easy way to go on adding Mg is Epsom salt as it is far cheaper and far easier to find at most any store selling health products or plant food.
this stuff confuses me because symptoms of Ca/Mg deficiency or overdose are basically the same from what I have read...

Would love someone to come in and clarify the best way to pinpoint specific symptoms for one vs the other

I stopped worrying about how to add Ca to my tank when I finally located the report of my town's water source and realized how much Ca is already in there. However the Mg levels seem to fluctuate depending on which month they tested in... so I add Mg occasionally, when the plants seem to show symptoms. I use epsom salt, very little- less than half of a 1/32 teaspoon for dosing 35 gal, and literally 5 or 6 grains of the salt for dosing my 10gal. I dissolve it well in the tank water and dose along w/my other dry ferts.

Only once a month, lately I've been doing it once every 5 or 6 weeks. Probably not a perfect method but results are better now for me...
this is good info... can you clarify exactly what 'symptoms' you are noticing to prompt dosing Mg??? Would not be surprised if I have a similar situation...

i find that adding Ca/Mg (one or both) or the ABSENCE of adding these can cause big issues for me. Sometimes I will dose a decent amount of both and be fine for a while. then I will run into severe plant issues and cut back. then it will be fine for a while. I have not been able to pinpoint a pattern here so it has been a guessing game for me... any info or shared experiences with this would be really helpful.
this stuff confuses me because symptoms of Ca/Mg deficiency or overdose are basically the same from what I have read...

Would love someone to come in and clarify the best way to pinpoint specific symptoms for one vs the other
Actually I am still confused about it too. I could very well be wrong in what I said above.

Because these past two weeks I have been paying attention to the gap of time between dosing macros and micros- I do so little I had been told it was ok to dose at the same time. I'm still dosing them same day, but now at least an hour gap between. Plants are looking much improved in my main tank. I wonder if what I had interpreted before as Mg deficiency was instead iron? because combining the macros & micros can inhibit iron uptake, correct?

Ferts are so complicated!

Pic of the symptoms- leaf paler between the veins- it shows up most often on my anubias:
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This is great info!! I'm still waiting for a call back from the city about how much Ca and Mg we have in our water. I have all the dry ferts I need (I got them in a bulk EI package) so I'm all set: just waiting on the numbers :)
Greetings from a fellow Minneapolitan! Here's the municipal water report:
Water Department - City of Minneapolis
Scroll down and look for "Monthly Plant Effluent Water Analysis" on the right side. I find that the Ca:Mg ratio in the reports is often in the 15:1 range, while I have read that 4:1 is the ideal ratio so I add some Epsom salts after every water change. Seems to be serving the plants well, and has cleared up the constipation on my pearl gourami, too!
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Ferts are so complicated!
This

i see MAJOR plant deficiencies/overdose symptons (severely stunted new growth, twisted new growth, discoloration, etc...) every month or so for seemingly no reasons at all. Making a drastic change in my dosing regimen seems to help out. I have never been able to get it stable for a length of time without having to adjust. these kinds of things always turn up every once in a while and cause issues.

in particular Ca, Mg, and micros are usually the culprits
I am wondering if you saw this thread where I was also trying to figure out if I needed to dose Ca and Mg http://www.plantedtank.net/forums/11-fertilizers-water-parameters/1109402-did-i-make-mistake-using-mg-do-i-need-add-ca.html Maybe some of the question/answer in there will help you.

My plants are doing better now.
Note what I am doing different since I made that post: I pulled out the cuttlebone in both tanks. I have only dosed Mg once since. I am leaving an hour or more gap between dosing macros and micros. And I have gone back to dosing the recommended amount of micros- just under 10ml on my 10gal betta tank and approx 30ml in the 38. (I had reduced micros after reading some threads about micro toxicity but now I really think the issue in my individual tanks was not staggering the macro/micro dose)

Bump:
This

i see MAJOR plant deficiencies/overdose symptons (severely stunted new growth, twisted new growth, discoloration, etc...) every month or so for seemingly no reasons at all. Making a drastic change in my dosing regimen seems to help out. I have never been able to get it stable for a length of time without having to adjust. these kinds of things always turn up every once in a while and cause issues.

in particular Ca, Mg, and micros are usually the culprits
Didn't you write a thread a while back that you were going to quit dosing on your tank altogether? How's the results on that... ?
(Need to go look for the thread if it was you- don't mean to hijack here)
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Thank you so much d33PVI! I was having a heck of a time finding the info! Because we purchase our water from Minneapolis, I couldn't get any exact information! I knew I was going to have to add Mg but I wanted to make sure I wasn't overdosing. :)

Also +1 to "Ferts are so complicated!"
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