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COCO COIR RO water & ph problems

4

416grow

New member
Hello,
I have purchased a RO water filter and have been having problems with my plants since I started to use RO water.

​​​​​I grow in Coco coir a 60/30 mix with perlite and I'm using the GH floraNova nutrients.

I would add my Silica first the the Calmag then test with PH pen and I would get a PH reading of 7.8 use ph down it get it to around 5.9 to 6.2

My main question is should I be adding something to the water other than Calmag to help stabilize the PH.

Here are some photos of the problems I was having. I ended up cutting the 4 plants down and you can see the roots were super white and very healthy not sure where I went wrong.


​​​​​​​Thanks
 

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When I change something in my grow that causes problems I tend to go back to what was working. Was there a problem that led you to RO water or was it something you read about and decided to try?
 
I just upgraded to the RO filter because all you read is RO water is the best for cannabis so at the moment I don't have any plants ready yet I have 4 autos that I started yesterday and of course I'm not going to use the RO filter for the plants untill I can figure out if RO water ok to use with Coco. So far I hear that if your growing in soil this is not a problem as the soil will take care of the PH.

What I'm hoping to find is some sort of ph buffer.
 
RO water is close to distilled, nothing in it but H2O. It is my understanding that RO is used when the starting tap water is very hard, and when the nutrient solutions are added the TDS is way to high. In that case, RO is used to supplement the tap water to lower TDS. Since there is nothing in it, when using all RO water you have to supplement with extra calmag. Coco needs extra calmag in the first place, so when the RO is factored in the required calmag supplement is even greater. Have you checked your starting and finishing TDS?
 
Are you adding sillica, calmag, lowering ph then adding floranova? Appears with the one atleast you're burning it up with something.

Id use tap you'll have less issues. Get a boogie blue filter for water hose
 
No I was adding silca then Calmag ,floraNova, then I would add Ph down, what your saying is to add the silica then Calmag then Ph down to close to what I want then add floraNova test ph and lower if needed.
 
Until you get some minerals in the RO water it's hard to pH. Your pH adjustment should be last. If you use a strong base (-OH) for pH down it can strip out calcium and magnesium.
 
Ok so here is a better exmple of what is happening.
So I have to buffer some Coco coir so I added CalMag to 400ppm if I test the pH at this point it reads 6.9 but if I move the pH pen just alittle the pH drops to 5.7 if I leave the water alone for 30 min come back ant test it's 6.9.
Bottom like us what if I was in DWC with air stones??
Unless someone can tell me that there is a product for RO water to add some sort of buffer to stop PH swings RO filter are not good for Coco coir growing.
Any info on this would be a great help

Thanks
 
Minerals of any kind. The pH number is a measurement of the electrical charge on atoms or compounds dissolved in the water. Some carry positive charges (H+) low or acid, some carry negative, high or basic (H- usually -OH).

You can try and pH the RO. Add a drop or two of vinegar and see what it does. Should swing way low. Add a small amount of bicarbonate and is should swing way high.

Then try and bring it back. You will find out with the pure of water you can change the pH back and forth with small inputs but is is such a weak solution it is quickly overwhelmed when mixed with other chemicals or into the soil. That's not to say it still does not affect the final result.

I was using MgCO3 mixed with rain as a buffering solution. It's normally nearly insoluble in water. But added to the fairly pure rain water (20 ppm and 6.2 pH best I can do using my Apera Ph 20) it will take about 30 mg per L into solution as Mg++, the CO3 goes out as CO2 and O- and raise the pH to a max of 9.7 where it is saturated and most falls out of solution. It takes about a 1/2 gram to a gallon/4L to max it out without solids any dropping out. This worked great as a buffering water to raise the pH of my soil grow stuck in the low 5s.
 
RO water would not be my first choice for coco, It needs extra ions to saturate the cationic binding sites, not fewer. Like 3B said, pure water is difficult to read pH, and is subject to large swings with small adjustments. pH pens are finicky, you must calibrate them before using it every time if you want an accurate reading. If you don't, you might as well just guess at it. The reading should be taken while gently stirring with the pen and after the reading has stabilized. Once you establish what you need to add for pH correction it will be less of a hassle when remaking solutions. I have been working in labs for years and am used to calibration requirements, but I dumped my pen for pH strips. They make life much easier. I think many people run into problems that have a root cause of pH being off due to inaccurate pens. The cheap ones are junk, and the good ones are expensive and need proper care to last. Always test pH last after everything else is added. pH will swing as things sit, air dissolves in, out, etc. Test your solutions going in and coming out of the pot. I get the feeling you are trying to micro manage the pH, and maybe you have not verified the accuracy of your pen, or you just have a cheap pen. pH adjustment is not a hard set value you want to maintain, but more of a range. The buffer that you seek is the dissolved ions that have been removed from the RO water.

This is what I use now-
https://www.amazon.com/Hydrion-Chart...%2C118&sr=8-19
 
Last edited:
Thanks for that great information I am using a Blue lab pH pen and I just checked the Blue Lab website and right on there site it says do not use Blue lab pens to check RO water or distilled water as it can damage the glass!!! So for now I have gone back to my regular tap water witch comes in at 150ppm ph 7.1 I'm going to post my findings as my grow shop who sold me the PH pen and the RO filter I should have known about this problem and it also says on the Blue lab site if you use the pen in RO water or distilled your 5 year warranty is void.
So I paid $350 for the RO filter and $140 for the blue lab pen (Canadian Dollars) but the pen seems to be working fine when I tested my tap water it was off by .3 I calibrated it last night but I did test the RO water this morning witch you said I would have to calibrate rack time so you were bang on with that.

I just want to say thanks for all your time and help with this is RO water problem.
 
Bottom line no problems at all just reading and wanting to just grow better and now I have learned the hard way but by making mistakes you only get better.
Thanks
 
Remember, the pH scale is logarithmic. The difference between 4 and 5 is not 1, it is 10. Between 4 and 6 is 100, etc.
 
RO would be good if you tap water is garbage or no access to rain water. You don't have to run straight RO you can blend it. Most 'purified' drinking water is RO water. It's good water you just got to know it's limitations and requirements.
 
I know that the rule of thumb is 6.0 feed water but, as has been stated, coco tends to be low in calcium and magnesium. I would get a soil PH tester and test the root horizon to see what's going on down there. I had a coco grow where my plants were doing the same thing. I had a soil PH tester and tested the root horizon only to find that it was registering at 4.8

I adjusted the PH on the feed water to 7.0 and fed the girls. After an hour I checked the soil PH and it had gone up to 5.4. Checked again a few hours later and got the same reading. Couple days went by before the next feeding and I, again, checked soil PH. 5.1. Did another higher PH nute solution and continued until coco was able to maintain PH at the desired level.

I was also feeding Cal/Mag at 1.5 times the recommended dosage until PH leveled then resumed normal dosage. Crop came out great!
 
Thanks for that tip the soil ph tester would be great this way you can get a good idea where the pH is at the root zone.

Thanks
 
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