[samiam]

I thank your right spaventa. Damn good thang I got those CMH lights.

[tleaf jr.]

If im not mistaken hydro runs a tad lower in the 5.5 range ...maybe 6.0 is to hi.

[moose eater]

I'm not familiar with growing in rock wool.

Anyway, if they're getting stressed from too radical a drying and wetting cycle, try some source of silica, if you're not already using one. And try to not let them get bone dry. Also, reduce the amount of run-off a bit. Excessive saturation fluctuating to extreme dryness may contribute to what you're seeing. "moderation in all things.. including moderation."

I recently included rice hulls as a part of what I used to provide in perlite. Rice hulls reportedly provide some silica, which can address some of the wet-to-dry-and-back-again stress, from what I understand.. I also use Pro-Tekt as a source of silica. (*Real -sand- here is scarce...).

Beyond that, the only other thing I can think of might be some sort of infection?

[samiam]

I use pro-tekt with every feeding. I made the mistake of adding extra Epsom salt to mix for a couple of days and it made the rockwool soggy like it was talking longer for the pots to dry out. Now I just spray the leaves.

Rockwool is kinda strange in that the first watering I give my plants right after a transplant they dry out really fast but it takes a little longer to dry out on the 2nd watering.

[Miraculous Meds]

Originally Posted by samiam

There in mini rockwool cubes, they get pretty dry in between waterings. My pH run off is 6.0, nute mix is 5.8 ph going in.

Theres your problem. As soon as rockwool gets well rooted, you have to keep it wet. The dry cycles should feel about 1/2 of fully saturated weight. When starting out in rw, its good to dry out more, but once roots are established, if you dry out real hard one time, you fry tiny roots, and create salt build up instantly. Increase your feed frequency.

[samiam]

I agree about not letting them dry out too much, but there is still a bit of wight to the pots when I water. I wish there were other growers using RW mini cubes to help me out, this is my 2nd grow using the mini cubes, I was killing it coco but my back can't take that shit anymore.

[Phaeton]

I clicked on this even though there were two pages already. This falls in the area I ran light spectrum testing on back when CMH was new.

Marijuana plants have to redistribute the size and types of chloroplasts in the leaves after any major change in spectrum, good, bad, or indifferent.
This causes a temporary droop while the growth cycle is interrupted and the energy put to rearranging leaf composition. The growth should be back to what it was, or better or worse, depending on the change, within weeks or less.
Most plants will grow under most lights as long as the spectrum is consistent, change is the awkward part.

Standard MH is pretty short on long wave red and very heavy on green and blue. CMH has way more deep red and a more balanced green, yellow, and blue spectrum. This does effect plants, generally in a good way, but the chloroplasts need to adapt to use the extra red.

Using a good balanced light spectrum from seedling to harvest will generally (generally) yield the best results.
Tailored trial and error systems using clones can dial in some extreme results but take time and effort beyond what is considered reasonable.
At least that is what I was told when using my dialed in rooms with the same clone for four years running. I got old and can no longer keep up so use seeds and generalized lighting.
It is all good.

[Phaeton]

Originally Posted by samiam

I agree about not letting them dry out too much, but there is still a bit of wight to the pots when I water. I wish there were other growers using RW mini cubes to help me out, this is my 2nd grow using the mini cubes, I was killing it coco but my back can't take that shit anymore.

I started using the rockwool croutons in 2001 and still do.
I have used a few brands of nutrients but settled on General Hydroponics three part for ease of customization and no need for supplements. Supplements have been tried over the years, epsom salts, silica, calcium, sulfur, combos for bloom...anyhow, none improved on the basic mix in extensive side by side testing. A special room was set aside for light spectrum tests and side by side nutrient tests. Other brands work as well, I just like GH3.
I still use 'Grower's Gold' Fulvic acid (79%) supplement at 1 ml/liter (4 ml/gallon) from seed to harvest. This is not a nutrient and at $300 USD per gallon a little goes a long way.

I flood and drain from the top for watering, this flushes the plant daily, preventing salt build up.
The 7 gallon containers get 3 gallons of water, the 3.5 gallon containers get 2 gallons. Approximate, just enough to float the perlite. Runoff is roughly half of the input, 1.5 gallons and 1 gallon respectively.
When ambitious the watering is every 4 hours, every 6 showed very similar yields. Once every 24 hours is functional but larger plants (4'+) showed less growth in side by sides versus every 4 or 6 hours.

Rockwool is not only ideal for roots, it is the absolute best media for bug eggs. To slow them down an inch and a half of perlite is used as a topcoat. It floats so stays in place and cuts the larvae count in the runoff by 80%. It also stops the algae layer from coating the surface.

Newly transplanted seedlings gets watered every 4 hours for the first week. The rockwool does not hold water when new and the top half will dry out in a matter of hours.
By the end of the week the rockwool will hold water for 24 hours and the schedule can be relaxed. Although water can be held for 24 hours, growth is enhanced by a bit more frequency.

[samiam]

Thanks phaeton, That's exactly what I'm trying to understand about the Rockwool mini cubes drying and watering frequencies, I do notice fresh RW doesn't hold much water in the beginning but over the course of a week it gradually holds more water.
That's what's making it hard for me when I set my pump times to come on I have to consider the extra water it will hold after a week.

I thank the bottom stays to wet with the mini cubes so I put a 1" layer of perlite in the bottom of the pots.

I do grow large trees I veg for 2 months. My last pot size is 7 gallon when I flip to flower, watering twice a day when lights are on. Do you thank it would be better to stay under 7 gallon pot size and do more waterings per day vs 2 in the 7 gal?

[WHIPEDMEAT]

rockwool cubes has two types, depends on the cut when it is made to pieces

one can be vertical with good drainage (Vital, Grotop Expert)
other is horizontal for better capacity of holding water in them (classic, Classic forte,Grotop Master) specially the last one has thicker layer on the top for more water