Grodan cubes and blocks are pH NEUTRAL

[AlphaPhase]

I'm new to using stonewool, actually just started using 4x4 blocks and macro plugs yesterday. But I've read alot about them.

One thing that comes out mind is that EVERYWHERE on mj forums say that blocks are acidic and raises pH. Well, it's actually pH neutral just like hydroton.

So this brings me to all the incorrect information about needing to soak the blocks in 5.5ph water for hours, or even over night. Who made this crap up? Lol.

All you need to do is put them in 5.5ph water, let them sink (takes 15 seconds or less) then you're done pre treating them. Or 30 minutes tops if that makes you feel better. Put the plant in and stop wasting time.

So just wanted to point that nonsense out. This should be a sticky so future stonewool users don't get sucked down the bs information tunnel.

 

[blackforest]

Rockwool is actually a little alkaline, aprox 7.8 ph, that is why they recommend using water at 5.5ph ish clones/seedlings like 5.8-6.5 area. I've never soaked mine for too long either.

 

[Aeroknow]

Yup, they are alkaline.
I soak them in 5.5 and not too long after, that nute solution they are soaking in gets up to 6.0+ in just a little while.

@AlphaPhase
Those new cubes you got might not be as bad as the regular ones. And I do believe rockwool has gotten better over the years in that regard also
You liking them things though huh?
I just got done dumping a bunch of 3x3's into a can of 5.5 nute solution, because I have to sink a bunch of cuts in a couple hours.
I always soak(5.5) for a couple hours at least. Its just a habit I got into doing a long time ago.

 

[AlphaPhase]

I'm just going by the grodan website, the stonewool itself is pH neutral but there is some residual lime from manufacturing that needs to be dissolved. I soaked x2 4" blocks in 5.5ph just until they sunk and for 30 minutes and I didn't get any pH change could be just the newer blocks but I think just soaking them in pH water until they sink and then saturate them with your nute solution is, A-OK! Lol, see what I did there

 

[adower]

I never worry about soaking my cubes at 5.5ph water. I throw mine in 7.8 ph water out the tap and never had an issue.

 

[AlphaPhase]

I never worry about soaking my cubes at 5.5ph water. I throw mine in 7.8 ph water out the tap and never had an issue.

Right on, I think all that really needs to be done is a rinse. Lime dissolves really quickly so you could just run tap water over the cube for 20 seconds and it would be gone. Then just dunk in your nutrient solution and your good to go

 

[Chillin chillin]

I've soaked so many cubes it's crazy, they raise the ph from 5.5 to 6.0 after soaking a box in 75 gallons of water. No way that's neutral.

 

[AlphaPhase]

I've soaked so many cubes it's crazy, they raise the ph from 5.5 to 6.0 after soaking a box in 75 gallons of water. No way that's neutral.

The residual lime from manufacturing is what is raising the pH, not the blocks, if you rinse the blocks for a few seconds prior to soaking, the pH will not rise. Just pretreatment a 72 case the other day, rinsed them soaked them for a few minutes (put them in the tote of water, then took the ones out I put in first). No pH fluctuations at all.

6.0-6.2ph

 

[AlphaPhase]

Rinse blocks with tap water for a second. Soak in 900ppm nutes at 6.06.0ish ph, plant the clone and watch the magic happen

The rockwool transition from hydroton has been a breeze. 1.4-1.6ec - 6.0-6.2ph - easy peasy

 

[AlphaPhase]

Oh, with that said. If I measure the pH of my tap water, it's about 6.4 - in 24hrs it's 6.8 and in 2 days it's 7.2ph with adding nothing to it. Waters pH naturally rises daily. But my blocks haven't been raising the pH of the water I use.

 

[Chillin chillin]

Like I said, when soaking 6" Hugo cubes(case is 4 the ph raises. Call it lime from whatever. Point is the ph rises after so many.

 

[AlphaPhase]

Like I said, when soaking 6" Hugo cubes(case is 4 the ph raises. Call it lime from whatever. Point is the ph rises after so many.

Do you mean it raises .5ph on top of the waters natural pH rise? Whenever I mix a res, before I use it on plants, I have to set the pH at about 5.5 because in a day it will be at 6.0 and rising for a couple of days, my pure tap water maxes out at about 7.8 in 3 days or so

 

[Chillin chillin]

When I soak cubes I add my solutions to my res @ 975-100 ppm 5.5 ph (55 gal res)
I make another the same but ph @ 5.0.
I then put an empty 55 gal drum in the middle of veg room. I place 6 layers of 6 6" rockwool cubes per later (36 cubes fit this way)
I then pump my nutrients into the drum full of cubes, soaking them as you go. Wait for all air bubbles to stop, then remove my cubes and place them where they go.
This raises the ph. I then refill w 5.0 mix and it balances to 5.5-5.6. Then add cubes and repeat.

 

[AlphaPhase]

Hmm, very interesting. You're getting that much of a swing just within a few minutes of soaking with that volume of water? Do you mind me asking what brand rw, grodan Hugo's? I haven't used those yet, but I soaked 72 4x4 blocks in about 12 gallons of water and got no swing, I'm using pargro quick drain. I do rinse them quickly though under the faucet, just enough until it's wet, throw them in the tote, then throw them in the tray. I'm wondering if my pargro are cleaner with less residual lime, because even when I didn't rinse them, and just soaked them quick in the nutrient water for a few minutes, I still didn't have a pH swing

 

[AlphaPhase]

Also, in the grodan hugo video tutorial, they literally just rinse them with a hose for 5 seconds, then dump the run off, that might save you a bunch of nutrient solution, just an idea. I'm always trying to save water haha

Also, out of curiosity, when your pH goes up that much, does your ppm? I know when I adjust my pH with pH up or down, the ppm is affected. If your ppm stays the same what is going on? Can you use lime as a pH adjusted that doesn't affect ppm, because that would be a game changer?

 

[Chillin chillin]

Ouse Hugo and pargo both. After I soak I don't water for like 5 days til roots pop out the bottom. I want them soppy wet @ 1st

 

[AlphaPhase]

Ouse Hugo and pargo both. After I soak I don't water for like 5 days til roots pop out the bottom. I want them soppy wet @ 1st

Yeah same here, it's my first go with rw so I took some time to get a feel for it and even weighed the blocks fully wet to get an idea when to water haha. 900g fully wet, water like 5-7 days later after transplant and they get growing. Seems to be working well watering when they are 1/2 dry at 450grams. I'm digging it, much easier than hydroton was and less work, never tried rw for 10 years because I couldn't clone for shit in rw so never even tried the blocks lol

 

[Chillin chillin]

I water for 1 min 10 times a day in flower. Are you hand watering?

 

[AlphaPhase]

I water for 1 min 10 times a day in flower. Are you hand watering?

I set up the flood tray after about a week from transplant, currently just flooding 1/2 way up the block 1x every 2 days. I haven't got to flower with rockwool yet, though. X

How far do you flood up the blocks, just the very bottom many times a day? That's how I run my hydroton suspended pots, I flood just a little up the mesh pot every hr to hr and a 1/2 in flower, but roots just dangle in air like aeroponics so I can't really over water.

Wasn't aware you can flood rw that much but your roots look good

 

[AlphaPhase]

I water for 1 min 10 times a day in flower. Are you hand watering?

Also, how much do you let the cubes dry out in the first week or two before watering again? How much should a late veg plants rockwool dry out before watering. Im assuming in flower to get it fairly wet but not fully wet?

This is all the roots I have right now, up until yesterday, I was just hand watering them, then I gave them their first flood. Not very many roots to what I'm used to with hydroton, is this normal? Was I not letting them dry out enough at first or was it because I was fully saturating the cube when I was watering?

Also, after a flood cycle, should the block be fully saturated or watered just enough to stay 1/2 to 3/4 wet?