Thank you!
I use automated watering. Specifically, I'm pouring water on top of the blocks for increments of 10 seconds about 8 times a day, starting an hour after lights on ending an hour before lights off water shots once every 2-3 hours.
Grodan, the company that makes the rockwool cubes,
hosts some documentation online that gives you instructions and formulas for how to calculate your ideal watering amounts. I started out by obsessing and calculating how many ML I'm giving per shot, but I've gotten a little more relaxed with it.
Here's some watering rules based on the Grodan documentation:
- During veg, you want short shots of water. If your plants are thirsty, add more shots instead of changing the shot size/duration
- During veg, you should aim for a little bit of runoff towards the middle/end of the day. Aim for 5%-10% of the block's volume as runoff
- During flower, you want long shots of water less often. You want to let the rockwool dry out a little more between waterings compared to veg
- During flower, you should be getting more runoff towards the middle/end of the day. Aim for 10%-25% of the block's volume as runoff.
Going over some of your other questions:
You can do either. If you get your watering automation locked down, you can get really big plants from tiny amounts of rockwool.
This video is a good example of someone growing respectable sized plants in just 3 inch rockwool. My last grow was only using the 6x6 "hugo" blocks (unfortunately hadn't found the 420autoflower scrog method yet), I haven't harvested but my plants are just as big as when I was growing in 5Gal soil pots and I'm sure I could've gotten them bigger with a longer veg time.
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With my newest run, I'm trying to do just 2 plants instead of 8, I'm gonna see how big they can get by being in 6x6 blocks stacked on top of the 8x8 blocks.
This should work out fine. Some people argue that you don't need to soak the original germination 1.5" cube in nutrients, just regular water, but I don't think it hurts to give them some feed right away.
PH doesn't need to be 6.0 exactly, I've been ranging my PH from 5.5 to 6.0 without much issue, usually I start and soak with 5.5
You can stack your 6x6 block onto coco or another 6x6 block, I'd recommend waiting until you see roots coming out the bottom of the top block and "transplant" by stacking and letting the top block dry out for a day while the bottom block is nice and wet. Afterwards, depending on whether you can see rooting in the bottom block/substrate you might want to continue watering from the top block for a week before you switch to only watering the bottom block and letting the roots wick up what they need into the top block.
Timeline based on previous posts in this thread:
- Around day 16 after germination you want to stake the main top down to allow the lower branches to catch up in height
- Keep the main top pinned down for a couple of weeks, adjusting the stake as needed
- The original instruction is the flatten the plants out and scrog about 5-7 days after seeing the first preflower pistils. Since we're growing photos, I'm not sure that this timing is as critical here, just make sure your plant doesn't get too tall for your space before you flip, you want to end up with enough "preflower stretch time" for the lower nodes to be able to hit and fill out your scrog net
I've tried both without issue. According to Grodan, if you stick the tube into the rock wool, you want it to be emitting at a 0.5GPH flow or less, otherwise the water pressure will be too strong and "create channels in the rockwool". For watering on top of the cube, I think most of the people in this thread are using the
FloraFlex FloraCaps which help redistribute water evenly when poured on top
Last note, for nutrients, I'd highly recommend CropSalts to anyone interested in new nutrients. I tried the GH Flora Trio for my first run, the feed chart had me running different ratios of their three bottles every week and I was constantly troubleshooting issues with my plants. I switched to CropSalts and I couldn't be happier. Same formula/ratio from seed to flower week 4, a different flower formula/ratio for flower week 4-8, and a third formula/ratio for the last weeks of flush. Also, my rez PH is a lot more stable compared to when I was using the GH flora trio. Super easy and has worked incredible for me in my first run with it