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Cal to MG ratios ,MG def

Hi UK420,

I'm hoping someone might be to offer some advice on the following.

Since growing i've had MG def Usually showing on Autos on the 4 th/5th week and in photos around the same time. with the rapid loss of leaves to follow.

My first counter to the problem was to add Epsom salts at Week 3 -5  this made some improvement but was still a big issue.

I then added Cal / MG in the form of Equilibrium , this actually made it worse.

My next step was to test the PPM of my Tap water which came out around between 250-290

Looked online at my water suppliers Information and stated it was a Hard water area.

My conclusion was that it was possible i was suffering CAL toxicity and in turn getting locked out of MG.

I Bought some TNT Bactorr in the hope the Bennies would chealate the excess in the water

I also bought some RO Water in the hope of starting with a clean sheet would be easier on my next grow  ,but soon discovered that RO water needs to buffered ideally with tap water.    (Haven't used the RO Water yet)

I Also changed Nutrients towards the end of my last grow From Plant magic Oldtimers Bloom (the newer thin one ) over to Bio canna flores In the hope that using a nutrient with lower cal might help the ratios of cal to mg

I also realized that i probably over watering  as personal observation on my last grow.  and that photo period plants i did last grow did suffer from mg def but i had time to rectify with Epsom salts ,where as with the autos they never seem to recover fully.

In that time i was looking for more alternatives , and was looking for hard water nutrients, well to my knowledge there aren't any hard water based organic nutrients ?

I seen the positive feed back given to Growers Ark on here and had look , seen they do water tests also noticed its salts based and therefor not organic which to be honest put me off a tad,but without any current alternatives i decided to buy the Soil starter kit but not before requesting the Water test , GA Who were extremely Helpful and i see why they have a good reputation on here. Completed the water test and sent the following info.



results are below values are in parts per million (mg/ltr) except pH which is of coarse in  the pH scale (-log of the concentration of Hydrogen ions if you ever wanted to know).

Calcium............64 ppm

Magnesium......6 ppm

Sulphate...........4 ppm

Alkalinity ..........280 ppm


This is a hard water.

Magnesium levels are lowish (range from 0 to 50+ with usual range between 2 and 20) and when compared to the amount of Calcium an ideal ratio of Ca to Mg is between 2.5 and 4 to 1.if your food does not have sufficient Mg this may cause problems assimilating enough Mg (essential to chlorophyll as Fe is to Haemoglobin).

If using our hard water soil food  with this water gives final values for Ca of 84 ppm and Mg of 28 ppm giving a ration of 3;1 which is good.

When growing in soil I can see no other issues with this water.  "


So basically not to much MG in water and by using GA Hard water nutrients i should be OK. but ideally i want to keep organic ,although some of my next grow will be done with GA soil kit

And with Bottled organic nutrients i guess i should be looking for a feed with high MG Or some sort of amendment to the soil? or of coarse i could just add Epsom salts through the entire grow adding to the water but I'm unsure how much i should be adding ?

Given the info provided above would anyone be able to give advice on roughly how much i should add and when ? when it comes to adding MG, I Guess this would also depend on what nutrient i used? at the moment i have the complete PM range Plagrons alga grow and bloom and Fishmix and Bio Flores when it comes to bottled organic nutrients.

As mentioned above i have 100 ltrs of RO water i was planning to use this on my next grow in the hope of eliminating what i thought at the time was high CAL levels now knowing its more to do with low MG , Will adding Tap water as a buffer still be a good idea ? i fear i would still have to add MG to the water because its not going to be in the Ro water and its not in the tap ?

Just about to start another grow and if its not obvious yet i've completely confused myself before i've even started.

To add to the confusion i also wanted to have a stab at No till style to see if that could offer a better, easier solution so bought 2x 15ltr Air pots and some organic soil Plagrons Royal mix along with the Dry amendment Supermix some worm casts , air pump, compost tea,etc its not real NO TILL in the sense i havnt sourced the individual ingredients ,to me its more about testing the style of growing and seeing if it could potentially be easier to combat my issue. and doing a small run actually works out  cheaper to buy the ready made Dry amendments ,if i see it has potential i of coarse would look to Either Buying  better Dry amendments Like Botanicare Growilla Or one of the Soil recipes on here  and  wanted to use the RO water for this grow . should i just bubble some tap water off instead ?given its not going to have much MG as stated above, i've since bought a large Britta water filter Would using this be better?

Apologies for length of topic i thought it was important to tell you as much as i could in the hope of getting a better solution. hopefully i've just fried my mind writing this and not yours

Thanks for reading Barry





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Pm is made for hard water bro, Im preety sure canna needs alot of cal/mg to o.d on so why is it not added to feed anyway or pm soil, seem to hear this problem alot, years ago I never had it or heard of it, but now its rife. Are the water comps removing it?? Idk seems too common nowdays,

You can folia feed with epsom salt if that helps sorry I got no advice for your mate but I feel your pain

Good luck

Edited by Kaoticnzymes
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