Need advice for rock wool set-up

[Jdogdabface]

Im setting up a new room and I'm giving rock wool a shot. I know what I want because I'm modeling this room off of another I saw and like very much. I just have a few basic questions someone may be able to help me with.

Ill be using 6 inch rock wool cubes, top feeding, not using a dripper, I'm using flora caps with flora clips.

I was going to water the plants approx 3 times a day for 2 minutes a feed. I read this somehere but what do you all think? Id rather the media get dry rather than risk it with a dripper.

Also, is there a risk of nutrient lockup with these cubes?

Do i feed nutrient solution every feed, or bounce back from reg water and nutrients like soil?

 

[Ganoderma]

You want to water/feed rockwool more then 3 times a day. You want to keep the rockwool moist, if it dries out between feedings ph levels can change and ppm/salt levels will rise. More frequent water cycles help to keep things in check with in the rockwool.

You do not feed/water rockwool like you do water soil.

 

[sdd420]

Focus on ph first then the plant can eat what it wants. Some nutrients are not available at different ph levels. It is so easy to get lock out with bad ph. Remember you can't overwater rockwool as long as it can drain. Consider going to a ebb/flow setup. You can automate it and leave for days at a time, a lot less work. Peace sdd

 

[TreehouseJ]

I'm a pretty methodical dude, and rockwool has given me a lot of trouble in the past. It can dry up really quickly if a pump fails killing your girls, it has a tendency to clump up and dry unevenly, it falls apart, it irritates my skin and sinuses, it needs ph adjusting, it has invited pests into my rooms.. I see dudes crushing it with rockwool slabs, and I envy the simplicity, but it doesn't seem very forgiving. I'd be interested to see a 6" oasis cube run. Oasis cubes > rockwool IMO.

 

[Sequitur]

I'm running 18 hugos on a 3x6 table under 2x 600w lights and yielding over 2oz/plant.
Flood and drain for 5 minutes once a day an hour into lights skipping occasional days earlier in the grow when the cubes are still heavy or I need to go out of town for a day.

 

[bearminimum]

Wow once a day for only 5 minutes? I guess the Hugo retains a crap load of water. Didn't expect that low frequency but the Hugo's are huge, hmm. Thanks for info.

 

[RoostaPhish]

Yes, if you use larger volumes of rockwool you can spread the watering farther apart. If you water it too much you will encourage algae growth and root rot. It is less common than with other types of media, but far from unheard of. Pythium is a common problem as well. A quality way to check for precise watering times is to actually extract a liquid sample from inside of the rockwool and then check this samples ph. When it begins to swing out of your desired ph range, then it is time to water again. I use table that are filled with sugar cube rockwool, and the 4" blocks are sunk an inch or so in. The whole table is covered with panda plastic. This creates a huge, oxygen rich slab. And it definitely doesn't need to be watered more than twice a day at peak flowering. The rest of the time it is only once a day.

 

[Principante 8]

Ahhh rockwool.. There's a few ways to go about it. We used to run 6"hugo blocks 4-6plants per 4x4 table and hitting 1.5-2lbs from each single ended 1kw hortilux bulb. Starting veg in the Hugos seemed to slow shit down so we started in 4x4 cubes then put those on top of the 6". In full bloom we never needed to water more than 4-5times a day with the larger plants. If you transfer a small clone to a Hugo block it won't dry out for several days. This is no bueno. I think in rw plants grow the quickest when the cubes are about 50-75%wet. Cube on top of cube is essential to maximize results. Put a clone in a 4" and a 6"and see for yourself which grows quicker. I like to think of a Hugo block as a movable super fat slab. With slabs almost everyone puts a small block on top, 3",4"etc. Although when the roots grow it will connect everything into being one unit, they are still separate in some ways. The top cube will dry first and the roots will wick water from the slab underneath using it as a reservoir in some sense. You can over water rockwool for sure, though it's not common in small blocks or blocks on top of slabs. Using the big blocks it's much easier to overwater.

Get a timer that works in seconds. The cheap ones are like $60. Water until the very first second you see water come out. Timing depends on pump size, length of lines, etc. Mine was 8 - 15 seconds on usually. These cubes hold 5-6 lbs of water by weight. Saturate cube and then wait until it's about 3lbs until you water again. Do this regardless of plant size. Once a day for veg plants and smaller flower plants (1-2oz plants) and 3-5 times for larger plants up to a half lb dry weight.

With a 3-4"cube on a slab you can water more freely with good results. Rockwool is a miracle medium in some ways. You can easily grow a 2oz plant in a 4x4 cube so it doesn't take much. Like soil, sizing the cube and plant size is a big deal. In coco it doesn't seem to matter as much. Seems harder to over water the coco than rockwool.

If you use a reservoir under the table and recirculate your mix then duration of watering isn't as important. It could be 30 seconds or 15 minutes, it doesn't matter much,especially when watering once or twice a day. Drain to waste is far superior and only takes a few small adjustments on the timer as the plants grow. Good luck

 

[Principante 8]

Forgot to mention one thing. Watering Rockwool from the top is way different than from the bottom. People that flood water more often because the cube doesn't get all the way wet usually. When you lift up the cube from a flood system you can feel the bottom is heavier. Rockwool wicks for sure but not fully, thoroughly or evenly. If the water goes 3" high and the cube is 6" it just doesn't quite waterlog the whole cube as much as a top feed does. I've also done nft which is great. Anyways every medium and style has pros and cons, but keep in mind 'Rockwool' is not just 'Rockwool'. When people give rockwool advice it should be specific to each system or grow style. I grew with Hugos every way possible I think and you can overwater, as I've seen in several gardens. The growers that overwater always say, "so and so told me you can't overwater rockwool so didn't worry about it." Then they call me over to diagnose, and I tell them so and so was full of it and they were obviously using a different method. Easy fix though.. Be careful with people that sound confident but don't give detailed advice. Us humans are so easily swayed by confidence.

 

[Principante 8]

Forgot to answer the food q. Yes nutrients every feeding at full strength hydro levels. It will be mucho beneficial to use 9" square pots. They flare out so the top is 9" but bottom is about 7". The cube fits nicely and is slightly elevated inside the pot because of the way the plastic flares out from the bottom. Regular pots are mostly flat and most tables don't have enough ridges to make a difference with cubes. Even though the bottom of the block has ridges cut into it, it doesn't offer sufficient drainage on its own and takes a lot longer to dry out. Both ways are OK but the faster the cube dries the quicker the plants will grow. This is a much bigger deal in veg or when growing small plants in the blocks.

 

[plutosmoke]

Like what principante says...

Its all about root mass, if you have alot of rootmass it will dry out quicker. I agree with what he say about 50-70 percent water in RW although 50% to me is borderline danger zone. If the RW get too dry, it will create dry zones that won't be able to rehydrate. You will be top feeding with the Flora flex so salt buildup wont be an issue as long as you feed long enough to allow a good amount of run off(assuming you allow the blocks to "dry up"). GL have fun

 

[Cadfael]

Pre soak at 4.0 ph, leave for 24 hours. Check pH to see 5.6

if you feed from top, I don't like the green algae that forms. Spray with 50% h2o and 50% h2o2 at 3%.

Also, I like to cover the tops. They sell little plastic things (expensive) that fit over the top. I bought some paper plates, fold over, cut diamond in middle and one cut to the edge. Viola! A cover top for pennies.