Help with rockwool drain to waste setup

Justin Freidman

Justin Freidman

Well-Known Member
Morning Everyone, How's everyone doing? I can't believe I missed this sub-forum, so now I'm finally posting in the correct place! Sorry for the huge story...

I made a post yesterday crying because I hadn't got my setup right. It's here if anyone wants to look. It's here: https://www.rollitup.org/t/about-to-give-up-on-this-had-enough-underfeeding.978754/

I was feeding them 0.5EC cal-mag and 0.2EC hesi grow nurtients - pH around 5.8-6.1 (3 calibrated meters show these readings) they're a month old, C02 is at 1000pm, Canopy temp 27 and RH is 70-75%. I was feeding from top twice a day. I thought they were doing amazing as I remotely monitor and make a time-lapse video here:


Until I made a visit to the room to find this, I was devastated. Basically my plants were showing deficiency issues and I had no idea why. (again I'm very new to this)


1.jpg 2.jpg 3.jpg 4.jpg

I foolishly thought drain to waste rockwool would be easy, just water it with the correct nutrients everyday and it'd be OK. I had no idea about run-off, saturation of the rock wool, etc. I went ahead and built what I thought was the ultimate setup (top of the range leds, c02, aircon, rh control, remote monitoring, etc) and then cried and nearly gave up when it didn't go right.

I thought they were under-dosed so yesterday I stupidly upped the EC to 0.9 by adding more nutes and then left for the day.

Anyway, I did some reading last night on rockwool drain to waste setups so visited my setup today to try and work out what I'm doing wrong. I'd really appreciate some advice and I will continue to read up on this and learn more, I'm sure I can dial this in now I know where I'm at.

So.....

This morning I changed my monitor to ppm(500) because I wanted to check the different between run off. The EC0.9 solution was correctly showing 430ppm and normal 5.9-6.2 pH.

20181030_101343.jpg

I then got a bowl and put one of the pots in to it and gave it the normal one minute watering. I threw my probes in to the solution and got this:

20181030_100819.jpg

I have 430ppm going in and 220ppm coming out, so I guess upping my strength yesterday was fine? Is there any figure I should try and target for the difference to dial it in more?

Also the pH is about 0.3 points lower - is this OK? It seems within range still, or should I up the pH to maybe 6.1-6.2 going in?

Now here's where I was definitely going wrong and could really ask for some advice, watering!...... I didn't realise how much water I was flooding the cubes with, so I got a measuring jug and checked. 2.2L of water per cube! Twice a day! I'm guessing that's far too much, even for the Grodan big mama cubes!

I've stopped watering for now and will leave a few days, then will maybe water them for 30 seconds or less once a day 2 hours after lights on.

Is there any method I could use for working out when to water these cubes? Or would it be best investing in a proper meter (like the smartbee) I really want to dial this in properly.

Sorry for the long post, I really want to get this setup perfect. Any help/advice would be appreciated.

Thanks,
J.
 
Airwalker16

Airwalker16

Well-Known Member
Yup, over watering. Rock wool is tricky and once you've saturated the roots they get complacent and stop growing. Try watering every other day. Let the cubes get almost dry first.
 
Deltagreen

Deltagreen

Well-Known Member
I'm not sure your room size, but if you're using 6" rockwool cubes then they should be on a tray. If you're are doing drain to waste then you should have a reservoir with nutrient solution to feed your plants with a drip line setup and another reservoir to catch your waste water. I would also go with solid feeding schedule with the right nutrients. Get yourself a timer that can be set to feed by the seconds. I grow with 6" rockwool cubes in a recirculating system. Check out my grow journal, I go into detail on my whole setup from start to currently in 7th week of flower. If you have any questions I'll try my best to answer them. Good luck, and happy growing:bigjoint:
https://www.rollitup.org/t/630w-cmh-sog-hydro-grow.975074/
 
fragileassassin

fragileassassin

Well-Known Member
I had some similar issues using rapid rooters in hydroton. I had moved my top feed too close and the moisture from the hydroton around the rooting plug was soaking into the plug keeping it dripping wet. quite easy to over water young plants and it can show in a wide range of ways.
 
Justin Freidman

Justin Freidman

Well-Known Member
Airwalker16 said:
Yup, over watering. Rock wool is tricky and once you've saturated the roots they get complacent and stop growing. Try watering every other day. Let the cubes get almost dry first.
Click to expand...
Thanks buddy. Should I cut down on the amount of water? 2.2L is a lot. Maybe half that and go every other day like you said?


Deltagreen said:
I'm not sure your room size, but if you're using 6" rockwool cubes then they should be on a tray. If you're are doing drain to waste then you should have a reservoir with nutrient solution to feed your plants with a drip line setup and another reservoir to catch your waste water. I would also go with solid feeding schedule with the right nutrients. Get yourself a timer that can be set to feed by the seconds. I grow with 6" rockwool cubes in a recirculating system. Check out my grow journal, I go into detail on my whole setup from start to currently in 7th week of flower. If you have any questions I'll try my best to answer them. Good luck, and happy growing:bigjoint:
https://www.rollitup.org/t/630w-cmh-sog-hydro-grow.975074/
Click to expand...
I'm using 8" big mama cubes. Grodan state they should be top fed only and not flooded. I converted an old flood and drain hydroton pot system in to a drain to waste - the cubes fit in the old buckets perfectly. I'm using a network programmable timer, so can select the time in seconds, days, etc. I'll take a look at your journal!

I'm just trying to dial in the watering schedule and also the ppm difference from what goes in and what comes out... :)
 
Airwalker16

Airwalker16

Well-Known Member
Justin Freidman said:
Thanks buddy. Should I cut down on the amount of water? 2.2L is a lot. Maybe half that and go every other day like you said?




I'm using 8" big mama cubes. Grodan state they should be top fed only and not flooded. I converted an old flood and drain hydroton pot system in to a drain to waste - the cubes fit in the old buckets perfectly. I'm using a network programmable timer, so can select the time in seconds, days, etc. I'll take a look at your journal!

I'm just trying to dial in the watering schedule and also the ppm difference from what goes in and what comes out... :)
Click to expand...
Ya. You need to find a balance to where the cubes actually have a chance to dry out, somewhat quickly (not giving them excessive water amounts) so you can water them again.
 
Justin Freidman

Justin Freidman

Well-Known Member
Airwalker16 said:
Ya. You need to find a balance to where the cubes actually have a chance to dry out, somewhat quickly (not giving them excessive water amounts) so you can water them again.
Click to expand...
I guess the scientific way to do that would be to use something like this:

https://store.smartbeecontrollers.com/handheld-water-content-meter/

I'm trying to run a remote room, it's an hours drive from my house, hence me remotely monitoring/controlling everything. I have 3 x 1000L tanks for drain to waste, just in-case I'm away from the country for a month or so.
 
Airwalker16

Airwalker16

Well-Known Member
Justin Freidman

Justin Freidman

Well-Known Member
Guys - silly question, I'm just remotely programming my timers to set up the watering... I know 1 minute gives 2.2L of water and I was doing this twice a day, which was 4.4L per day, far tooooo much.

Do I go for 60 seconds every Mon, Wed, Fri - or, should I go for small amounts every day, i.e. 8am (two hours after lights on) - just 15 seconds? Which is about 500ml / day? Or even maybe that's too much? Maybe just 5 seconds per day? ( around 300ml)
 
C

calenk

Member
too much rockwool for the size of plant...
you should be able to water them for even 15 minutes if you wanted. but you'd need less rockwool so it's significantly dryer the next day. That cube would take way too long to dry out with only that tiny plant feeding off of it. that will lead to all kinds of potential salt build up and root rot issues.
 
Justin Freidman

Justin Freidman

Well-Known Member
calenk said:
too much rockwool for the size of plant...
you should be able to water them for even 15 minutes if you wanted. but you'd need less rockwool so it's significantly dryer the next day. That cube would take way too long to dry out with only that tiny plant feeding off of it. that will lead to all kinds of potential salt build up and root rot issues.
Click to expand...
Apart from using 6" rockwool cubes for my next grow, anything I can do now? I've let them dry out for a couple of days now and tomorrow will just start feeding them about 150ml / day.
 
C

calenk

Member
Justin Freidman said:
Apart from using 6" rockwool cubes for my next grow, anything I can do now? I've let them dry out for a couple of days now and tomorrow will just start feeding them about 150ml / day.
Click to expand...
they'll catch up to the size of the cube eventually. maybe just take these other lads advice and feed a little less but keep in mind that small amounts of water could could build up salts so perhaps some flushing would help with that.
 
Justin Freidman

Justin Freidman

Well-Known Member
calenk said:
they'll catch up to the size of the cube eventually. maybe just take these other lads advice and feed a little less but keep in mind that small amounts of water could could build up salts so perhaps some flushing would help with that.
Click to expand...
Great, thank you. I can't wait to do my next grow. I'll go 6" grodan (then maybe double stack them) with a proper moisture probe monitoring system and a system for measure run off (including ppm/ec) and dry-back. I want to do this perfect.

I'm going to build a system like this: http://www.circuitstoday.com/arduino-soil-moisture-sensor
 
C

calenk

Member
Justin Freidman said:
Great, thank you. I can't wait to do my next grow. I'll go 6" grodan (then maybe double stack them) with a proper moisture probe monitoring system and a system for measure run off (including ppm/ec) and dry-back. I want to do this perfect.
Click to expand...
that's pretty cool. your setup is pretty awesome.

I think the key to rockwool is to progressively match the amount of substrate to the size of the plant.....imagine a tiny plant in an 8 inch block, in order to keep the salts flushed out properly you would have to water it a ton, way more than a little plant needs. remember runoff is key. thats one reason rockwool grow cubes are nice, cause you can keep transplanting into bigger pots as needed. nothing wrong with 8 inch blocks they just take a lot to keep flushed correctly.
 
Justin Freidman

Justin Freidman

Well-Known Member
calenk said:
that's pretty cool. your setup is pretty awesome.

I think the key to rockwool is to progressively match the amount of substrate to the size of the plant.....imagine a tiny plant in an 8 inch block, in order to keep the salts flushed out properly you would have to water it a ton, way more than a little plant needs. remember runoff is key. thats one reason rockwool grow cubes are nice, cause you can keep transplanting into bigger pots as needed. nothing wrong with 8 inch blocks they just take a lot to keep flushed correctly.
Click to expand...
Thanks dude. Understood. I think to be honest I just went overboard buying the big mama's when the 6" cubes will do me fine. Can I start in 6" cubes, or should I go with starter cubes, then in to 6"?

How important is run off (this is the actual amount that runs off when feeding - right?) against dryback?

i.e. if I use a proper meter to get my dryback to perfect percentages when it gets first feed and when lights go out (I read somewhere that between this time it's important to get the right dryback) then I could pretty much gauge it so I have minimal run-off and minimum waste?
 
You must log in or register to reply here.
Top