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Ph dropping in rockwool runoff

Hi not sure if had been asked about but can't find any info..


Can anyone help with the pH in res being fed is done to 5.8-6.2. 

The run off seems to be going as low as 4.5 is there a reason? Am I doing something wrong overfeeding to much or something? Any help would be appreciated



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What are your numbers for EC/TDS in and out?


What week are you in (I assume you are in flower?)


What temperature is your nute solution at?


What temperature is the air in your tent?

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Hi MicroDoser,


Right... Ec going in is 1.2-1.3 coming out 1.4

             Coming up to 6weeks flower.

             Nutes solution is between 18-20 'c 

             Temps are around 26-28 lights on and                   22-23 lights off. 

Plants look really healthy. Just a mind boggler as been told pH should be higher than the 5.8 putting in? Also been told could be irrigating to much so not getting the dryout time. Have tried longer times but again still coming out low... But then see when using rockwool some irrigate in shots up to 6 times a day. So bit confused 

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It may be that they have just reached the point where they are starting to slow growth and do not need quite so strong nutes. It may be they have been overfed and need their medium flushed a bit.


Your EC being higher on your runoff that what you are feeding them is a sign.


I would reduce the nute strength to 1.0 or less, until your runoff EC is the same or lower than what you are feeding them. Then start to ramp it up slowly being careful it does not rise above your 'in' EC.


The plants will look really healthy. After all, they have more nutes than they need. They will look just as healthy with lower nutes though, and they will grow quicker at 95% strength than they will at 105%...

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I see.. is it wrong then that when you say your feeding ec 1.0 your run off should be .1 .2 higher than 'in'?? 


I was told to read run off by if run off is lower more nutes required intill you get the .1.2 higher than what's being fed?? 


Also when I sort the EC out will this sort the pH run off problem out? 


Do you know best way to feed rockwool? I'm using an auto feed system. Is one, two feeds better or like 4-6 through lights on? 


Thanks for the reply mate. 

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I don't run rockwool but from what I have read, more feeds per day stops salts being dried onto the rockwool, which can cause high EC runoff.


I would say it would be a good idea to reset your rockwool.


Get a low EC, high PH solution (like EC 0.8 PH 6.5) and flush that through your rockwool until the runoff is in the ranges you want. Then feed as normal, but more often and see if the issue returns.

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Thanks for the help, appreciatd..


I'll try that and see what happens. 

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