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A Little Help Please...


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Ok, last friday I bought some grodan starter plugs and some bigger 3x3 cubes. I washed the rockwool with water ph'd to 5.5 as the instructions stated and put my babies in. 2 days later tap roots were at the bottom so I placed them into the bigger cubes, again 5.5 wash as the directions state.Today I added 1/4 strength fox farm grow big and ph'd to 6. Just for kicks I ph'd the runoff and it is reading 7.7. I am hand watering the cubes as they are just sitting in a propogation tray and hopefully into Hempys soon. I placed the probe into the top of the cubes and get the same reading of 7.7 The first single blades are twisting a little bit, just enough for me to be concerned. My question is how to correct this problem. This is my first experience with rockwool and any help would be greatly appreciated. :)

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im lost :)


if you are testing the runoff of your rockwool cubes then you are SOAKING them :( not good.


you could have went straight into hempys after the roots started coming out of the small block.


those "building type" rockwool cubes, where one fits into the next and so-on are normally for NFT or other kinds of hydro.

you can just use 2x2x2 cubes or whatever and then when they root, go straight into the hempy bucket.

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I used the bigger cubes merely as a better base of support before going into the hempys. WHy is hand watering the cubes over a sink until there is some runoff a bad thing? THe cubes can only hold so much which from what ive read is the perfect ratio of water/air. After they drain I place them back in the tray. My q was about ph adjustment. The feed water is ph'd to 6 but the runoff was reading 7.7. Is that a bad thing? If it is what should I do to fix the issue?

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just trying to help :)


first off, hydroton holds the perfect amount of air/water. not rockwool.


keeping a rockwool cube soaked is not good. it is no different than constantly flooding a dirt/soil plant continuously.


rockwool is used because of its unique ability to retain water.... but it DOES retain too much water.


rockwool should be kept damp, not soaked. a soaked cube contains zero oxygen..... until it dries out some.


depending on how big of a hempy bucket you are going into, that huge cube is going to crush all your perilite, allowing less oxygen into the mix, and making your roots have a troubled time moving around.


your plant stability comes from the roots attaching to the perilite foam balls, not from the rockwool cube.



testing run-off water, as you have done, is a method for testing soil basically. clean nutes/water go in the top, they filter through all the other nutes/bacteria in the soil, and then out the bottom it comes.


not the same for rockwool. its a "dormant medium". there is no other nutrients/bacteria in the rockwool to change the ph of water


i wouldnt be concerned with your findings, but i would get them into their permanent home soon.

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