Rising runoff EC in rockwool, how often do you flush your rockwool?

[HendrikO]

Hi,

I am using rockwool as a growing medium and feed top drip, drain to waste (same as TheCapn is doing with Airpots filled with very small rockwool cubes)

I water 3x a day, just enough so I get 15% runoff per watering.

The plants are currently 3ft/0,9m tall and I give each plant 200ml per watering (runoff included).

They are not transpiring a lot at the moment due to low temperatures (19° C / 66° F).

In late blooming I am feeding them EC 2.0 / PH 5.7-6.0 (Tapwater has EC 0.3 to begin with).

Currenly my problem is that the runoff EC is gradually rising from EC 2.0 to EC 2.7 within 1 week.

My idea to get rid of this problem is to flush with a mild nutrient solution (EC 1.3) at the end of the week to reach EC 2.0 runoff again.

Or would you recommend using me a flushing agent instead?

Furthermore I really doubt that I feed the plants too many nutrients.

I used to grow in hydroton in the past and was feeding the same EC during late flowering and never had issues with a rising runoff EC.

Or am I just wrong and I really have to feed a lower EC.

I just believe that I have to flush the rockwool regularly to avoid nutrient/salt build up.

What can you recommend me? How often are you flushing your Rockwool to prevent nutrient/salt build up?

 

[latewood]

Do not use a flushing agent during the bloom phase. Never until flush.

It is a fact that when your solution is gaining PPM that the plant is not taking as much during feeding. In general the fix for this is to run a lower strength solution as you mentioned.

It does not hurt to flush the medium once a month with PH'd water. No nutrients.

You have already figured out both methods. Beyond that; It is a trial and error. I would flush all with plain PH'd water, and then see if the issue re-occurs.

 

[c526]

can I get a picture of your set up,I am a Capn style grower

a 3 ft plant needs way more than 200ml of fluid 3 times a day,for this growing media (RW)

I would guess that your not getting the old nutrients out of the croutons,because there is not enough top feed happineng.

Capn style croutons rely on the top feed to be recirculated,if you just have the pump on for 15 minutes a day,it will go though 40 gallons of
solution/ water
thus rinsing the rockwool and keeping them clean.

flushing in rockwool(these ones) is done by preparing plain water to 5.6,run it through a 5 minute cycle,dump it,then add your water and nutrients to the new rez run for 10 minutes,done.change water again

never use a flushing agent in mid grow,(with RW) it will make you hate your life.

you have to get those plants to recycle more water,I have a plant on 5x15 minute,water cycles per day,that pump is a 185gph,so in 75 minutes of run time that thing recycles 200 gallons of solution over the roots and rockwool,it sits in a 15 gallon tote filled with 12 gallons of solution
she consumes 2 gallons a day.

good luck man,like to see another Capn style on board

 

[latewood]

If you are getting a 15% runoff, then you are applying the correct amount of nutrient solution. This is why I did not mention any doubts as to your quantity of solution. Your pump should apply nutrients every hour. And I agree; Recirculation will allow you to have a control reservoir. As long as you are always applying correctly PH'd nutrients, you will be OK. A good benchmark is 15 minutes on, 45 off. Do this every hour of "lights on" Never during "lights off". Adjust according to size of plants, age of grow and flowering plant needs.

I do agree that a picture would help us all give you a much more educated recommendation. Peace

 

[c526]

hIGH Latewood,for this posters inquirys,the advice is good,but not for Capn style,her is a link to his system
How to: Simple Hydroponics

for the rockwool blocks 15 0n 45 0ff is good

but capn style with the mini croutons,they cant handle that kind of water

 

[HendrikO]

Hi, first of all thanks for all your help.

I had a recirculating system before and was happy with it but I am trying out a dtw system for the first time now.

I believe that dtw offers more advantages than a recirculating system and hence I would like to stick to it.

My system is vertical, 12x 6l Airpots placed in a donut sytle on trays and the plants climb up a fence shaped like a cylinder.

This is the first time I grow vertical, once I finish this grow and finish weighting the buds I will post some pictures of my system as I have never seen a similar one before.

The only inspiration I got from Capn was to use Airpots filled with these mini rockwool cubes and top feed drippers, everything else is different in my system.

As written before I grow 12 small plants instead of one huge one and I grow vertical not horizontal and dtw.

Furthermore I am interested why you are not recommending to use a flushing agent before the final flush?

Even GHE states in their nutrient plant to use FloraKleen before the final flush from time to time.

Coming back to my problem:

I posted my problem on ----- too and another grower suggested that the rockwool is drying out too quickly and hence salt built up accumulates.

There might be some truth in this, I will try watering four times per day and see if the problem persists.

However I was researching more about my problem and it seems that I just have to flush rockwool at least every two weeks or even better each week to prevent salt built up. Usually I flush (phed tap water + flushing agent) only once at the beginning of flower, then after four weeks and one last time, a week before harvest. Doesnt seem to be sufficient though... I will try to flush every two weeks with a mild nutrient solution instead.

@c256: As my system is dtw I simply can not afford to run gallons of water through my plants. As I remember Capn only watered once per day at the beginning of the light cycle and even recommended only watering once?

 

[c526]

My system is vertical, 12x 6l Airpots placed in a donut sytle on trays and the plants climb up a fence shaped like a cylinder.

This is the first time I grow vertical, once I finish this grow and finish weighting the buds I will post some pictures of my system as I have never seen a similar one before.

Colosseum style?? there are growers who do that and hang a bulb in the center

@c256: As my system is dtw I simply can not afford to run gallons of water through my plants. As I remember Capn only watered once per day at the beginning of the light cycle and even recommended only watering once?

that is whats recommended,but its on to each individual plant.I have one going now that consumes 2 gallons a day and gets feed up to 6x15
I have tried exactly what you are doing,and the trouble I did have was a salt buildup.its why I say ,not nearly enough runoff

why can you not capture the dtw and reuse?? even my little clones get the same nutrient all week,it just recycles,


As written before I grow 12 small plants instead of one huge one and I grow vertical not horizontal and dtw.

---- 12 or 1 or 100 rw is rw
Furthermore I am interested why you are not recommending to use a flushing agent before the final flush?
--because it strips everything in it,it smoked me and Thecap and a few others here. straight water will do as you want,but if you cant recirculate,then that wont help

Even GHE states in their nutrient plant to use FloraKleen before the final flush from time to time.
-all ya can do is try,let us know how it works---the back of the bottles are useless,they sell product more you use more they sell.
If this was a free world,and we were able to know each other,I have 2 gallons of florakleen you could have

 

[HendrikO]

I dont have a colosseum style, it is a donut style, 12 plants in a circle (on the same level).

There has to be a way to make DTW work without or with minimal salt build up.

I will just try flushing my plants once at the end of the week when I change my reservoir.

I wont use a flushing agent for this as advised by you, just a mild nutrient solution.

I dont want to flush with straight tap water as I read that shifting the EC of the Rockwool/Root Zone too much is not any good.

I flushed with straight tap water during my last grow in the middle of flowering and the PH rose to 6.8 because the EC in the root zone was too low and my plants were starving.

When the EC went back up after 10 days or so I had normal PH values again.

So hence I wouldnt recommend flushing with pure tap water (except for the final flush).

 

[c526]

I cant wait to see what your building on,sounds interesting



ph the flush water for rock-wool it has to stay in the 5.5-6.1 ,I will be honest,its tough until you can get more runoff,not saying impossible,but tough for sure,I only tried it on 4 plants,I didn't have the patience to hand feed that many times

 

[latewood]

hIGH Latewood,for this posters inquirys,the advice is good,but not for Capn style,her is a link to his system
How to: Simple Hydroponics

for the rockwool blocks 15 0n 45 0ff is good

but capn style with the mini croutons,they cant handle that kind of water

OK cool. I did not notice that he was locked into that type grow. I do not do that, and won't due to this very issue with watering.

 

[Greenthumb J]

OK cool. I did not notice that he was locked into that type grow. I do not do that, and won't due to this very issue with watering.

There's no issue with watering.. a 6L airpot is too small for a 3ft tall plant, why cant anyone get that? Go get a measuring tape and see how big 3ft is.. then think of how much root mass is needed to grow a plant that tall.. then ask yourself if 6L of medium is enough?

A picture of the plant would really help a lot.

TheCapn only waters ONCE a day.. by hand, and to waste, in veg, and recirculates in flower via a water pump. once a day, thats it. Any more irrigations and you are risking high levels of potassium in your medium which can potentially lead to a calcium lockout.

if your airpot isn't feeling lighter within 24 hours of the last watering, the pot is too big, if its sucking up the water in 12 hours, its time for a transplant.

When flushing your rockwool (sorry c526 brother!) you dont need to balance the pH into range, since you're going to give it a fresh reservoir of nutrients. I've flushed a few plants to know that the rapid change in pH isn't bad unless you LEAVE it that way.

But, with Capn-style, as long as you are following his methods, you shouldn't be experiencing these issues. Once you deviate, thats when you run into troubles.

Anyways, not to knock my fellow Capnstyle brother c526, i know he grows some chongers, and i got mad respect for him, but this style is super easy, grows the biggest harvests on this site, hands down, and seeing TheCapn's harvest pics every 15 days or so, its crazy why people would want to grow in dirt!!

 

[c526]

all good greenthumb,Im glad you jumped in,your explanations of the style is waaay better than how I can get the thoughts from my heads to my fingers

 

[Greenthumb J]

Yea but all that really matters brother is how you get the knowledge from your head to your plants, which you got down!

 

[XiwsX561]

If you ever watch jungle boys you tube videos their medium which is 6 in rockwool cubes from start to finish and they'll get some genetics medium up to ECF 6.0 that's insane. You need professional equipment to monitor that. It's also based on the frequency and the amount they're being fed I think it's something like just a couple milliliters every 20 minutes throughout the day it's like six times a day or something but they also have perfect environment lab settings.