How often should I water with rockwool & ebb & flow?

This is the first time I'm going to use rockwool cubes. I have a very simple ebb&flow. I also have 2 layers of coco grow mat under those. They are about 1/4 inch a piece. The rockwool cubes are the 4 inch ones. I used To use expanded clay and I needed to water 3 times in a 12 hour period. I know rockwool retains water so I'm thinking maybe 2 times in a 12 hour period. I don't know, does that sound right? My temp is constant between 69-75, but my humidity level is low. Any help would be appreciated. Thanks.

twice a day should fine just keep an i on them
watch and see

budman52 said:

twice a day should fine just keep an i on them
watch and see

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Twice a day might also be way too much.
I used 4" rockwool cubes on top of a coco mat, and my biggest problem was overwatering. I was watering as infrequently as every 3-4 days. At te MOST I was watering 1x a day, and that was during peak flowering.
Of course this could be completely different with you. I would just watch them the first couple days and when they are almost as light as before you wet them, then water them. I have since switched to 6"pots filled with minicubes, but am thinking of going back to cubes on a mat due to cost. (mini cubes are stupid expensive)
Also should add, that the problem I had from over watering was root rot, and lack of root formation ultimately leading to small plants.

2x a day way too much in the beginning. Start at once every 3-4 days, tapering to about 1x a day in flowering. Really easy to over water with pure rockwool.

Correct me if im wrong but once a good amount of roots have grown the rockwool doesnt need to be wet as much and you can flood just under the rockwool bottoms more frequently? I left my cubes sitin right on the flood tray and once a good amount of roots came out I put them in hydroton to begin the more frequent waterings.

So I'm seeing 1-2 times a day. Thanks

Pure rockwool is not real well suited for ebb and flow. drip irrigation is a better choice as there is more control of the amount of saturation of the wool. If you use ebb and flow wait till the wool is almost dry to flood. Bigger cubes take longer to dry. If you start to see a brown slimy coating on the stem where it goes into the wool, stem rot is setting in and they need to dry out well.

kpw555 said:

Pure rockwool is not real well suited for ebb and flow. drip irrigation is a better choice as there is more control of the amount of saturation of the wool. If you use ebb and flow wait till the wool is almost dry to flood. Bigger cubes take longer to dry. If you start to see a brown slimy coating on the stem where it goes into the wool, stem rot is setting in and they need to dry out well.

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Good info. Would the small rockwool cubes have this problem? I imagine not as my stems devoured my mini cubes last time round but this time my cuts are in 4x4.

holy shit bro, before you do anything check out my threads and read what guys have been tellin me. I have 6 4inch rockwool cubes in an ebb and flow tray. check out the pictures..my tray is covered. i got shitty advice tellin me to water once a day.....WRONG!! you'll drown your shit. I have been watering every 3 or 4 days.. and i think that may be too much. I put them on a coco mat to help drain the cubes.. they stay wet for days with small plants. i wouldnt even fill your resivoir because the cubes need 2 cups of water every four days. i almost killed my plants watering everyday. check out my pics and threads..the plants are comin back now because of my new watering schedule. my room stays at 80 day and 70 at night. I would honestly water them once a week at 500 ppm. hit me up if you have any questions...contact me... i watered monday and i dont think im even going to water then today.

todays pics thier comming back at a every 4 day water

i threw away like 25 gal of mixed nutes fuckin wasted now i have a 20 gal batch that i going to toss out soon. bummer man thet dont need ebb and flow till you get mad roots out of the bottom of the cubes than the plants wont rely so much on the rockwool ..... i couldnt find any info on rockwool but i plan to spread the word.. wet conditions =slow growth

2 times a day.

just remember every setup is different!!!!!! rock on

onefortheroad said:

just remember every setup is different!!!!!! rock on

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Very true. I have 11 sweet peppers in 4" rockwool and 11 sweet peppers in 3" net pots; all buried in hydroton and silica stone in a 4'x4' flood and drain. I flood 4 times a day for 15 minutes. They look great and have wll over 100 medium size peppers on so far.

Once your roots form a carpet below the rocks it's no different than an NFT or DWC system with your roots wet all of the time. If the roots dry out, you will have problems.

But I agree, in the beginning when the plants are small, less watering is better until the plants get mature enough for good root structure.

Go Green...Grow Green

Thanks for all the info guys. I just pulled the cubes out of 24 hour soak and put some clones in there. There pretty wet and I won't have to water them for a couple of days. I have 3 layers of the 1/4 inch coco mat underneath the cubes for root growth. I definitely don't want to overwater for obvious reasons. I figured with 3 layers the cubes will sit high and they'll mainly be used as a support. For right now I think hand watering is the best. This is hydro so I would like to explosive root growth, but is that possible with this? I know when everything gets going it will be fine.

CookieMaster said:

Thanks for all the info guys. I just pulled the cubes out of 24 hour soak and put some clones in there. There pretty wet and I won't have to water them for a couple of days. I have 3 layers of the 1/4 inch coco mat underneath the cubes for root growth. I definitely don't want to overwater for obvious reasons. I figured with 3 layers the cubes will sit high and they'll mainly be used as a support. For right now I think hand watering is the best. This is hydro so I would like to explosive root growth, but is that possible with this? I know when everything gets going it will be fine.

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You will get explosive root growth. just follow the advice and not over water early on.

dude..i dont think over watering was yur problem there...and pics from later in the grow?...
I have a similar setup and i flood about a 1/4 inch up the 4 in rockwool cubes that are sitting on top of a 1/2 coco matt.. they seem to be triving ..i dont have any yellowing yet and lot of growth these pics are from day one to week 2

cool under canopy shot

wowzerz said:

Twice a day might also be way too much.
I used 4" rockwool cubes on top of a coco mat, and my biggest problem was overwatering. I was watering as infrequently as every 3-4 days. At te MOST I was watering 1x a day, and that was during peak flowering.
Of course this could be completely different with you. I would just watch them the first couple days and when they are almost as light as before you wet them, then water them. I have since switched to 6"pots filled with minicubes, but am thinking of going back to cubes on a mat due to cost. (mini cubes are stupid expensive)
Also should add, that the problem I had from over watering was root rot, and lack of root formation ultimately leading to small plants.

Click to expand...

this is the truth right here! im having the same problem as we speak and now im gonna test out these jiffy coco cubes someone told me about

Just some food for thought guys, I noticed that some of the people that have problems with over watering have the top of the tray covered or the rockwool is covered on the sides (obviously to stop algae) and there is not a lot of room for the rockwool to breathe. IMO if your having problems with over watering you may want to adjust the amount of time the tray is flooded, also stripping off a little of the plastic on the bottom of the rock wool will allow it to breathe. IME I flooded the tray until just the very bottoms of the cubes are getting wet which allows the rockwool to wick the water instead of being saturated. Also when I grew that way I used to use 4 inch cubes stacked on 6 inch cubes which absorbed the water and allows the 4 inch cube to "wick" water up into it. I hope this gives some ideas to help solve your problems, good luck and happy growing.
KnB