First time with rock wool.

[Chabnoc]

This is my first time useing rock wool. Seems to be working pretty good so far, but the PH is going up each day. I am useing R/O water, and I ph it to about 5.5, by the next day it is up to over 7.0. It is only been 3 days now. Is this normal, and if so, we it get better with time? I am useing the same nuts as I used the last time, and my PH was real stable.

Thanks for any help.

Chab.

Chabnoc Reviewed by Chabnoc on 06-12-2007. First time with rock wool. This is my first time useing rock wool. Seems to be working pretty good so far, but the PH is going up each day. I am useing R/O water, and I ph it to about 5.5, by the next day it is up to over 7.0. It is only been 3 days now. Is this normal, and if so, we it get better with time? I am useing the same nuts as I used the last time, and my PH was real stable. Thanks for any help. Chab. Rating: 5

[LOC NAR on probation]

What kind of system are you running ? Did you PH the rockwool for 24 hours before use ? Why did you switch to rockwool ? So many question but not enough time. More info, more help. It should get better with time though.

[Zandor]

Ya loc nar has it right. You must pre-soak rockwool at a Ph of 5.2 to 5.5 for 24 hours before you first use it or you will have the problems you are now having.

In hydroponics you do need to adjust the Ph several times a day too that is normal.

[Chabnoc]

I used something called Super Natural Rock wool conditioner. The instructions said to NOT soak any longer then 20 minutes, so I did. I only have to adjust once or twice a day. It is not that bad. But I was thinking that in the time span of a week or so, it should level out and get better.

What do you guys usually use for your grow mediums? I use a Flood & drain system.

The medium I have used before is pretty messy, even after you wash and rinse and wash some more. I was picking crap out of my plant tray for 2 weeks. And cleaning it out of my res.

[Chabnoc]

My last grow. I pretty much only had to ph my res when I replaced the water/nuts. It stayed pretty much where I put it for a week. Pretty much...lol

I think next time, I will soak my rock wool in PH'd water for 24 hours, then add the rock wool conditioner for an additional 20 minutes, after PHing the water again.


Thanks for all the help you two.

[Al B. Fuct]

Chabnoc, I also have to adjust pH down frequently. I do all the prep that Zandor and LOC NAR both describe for the rockwool cubes and a bit more; I flush my cubes under running tapwater before doing the pH 5.0 24 hour pre-soak. Along with my controlled clonebox conditions, this gives me utterly reliable strikes in 6-7 days.

However, I use loose rockwool floc in pots in my flood trays. It's simply not practical to soak and drain 23 8" dia x 8" tall pots of floc. I'm told (but haven't confirmed) that rockwool has some limestone residue left from manufacturing and this is what causes pH to jump up.

For me, it's no more trouble than adding about 5-10ml of pHDown sauce to my 125L tanks every couple of days to bring the pH down to about 5.3-5.8.

Please have a look at the link to 'A batch of clones in rockwool' in my sig. May or may not be anything useful for you in there.

[Al B. Fuct]

My last grow. I pretty much only had to ph my res when I replaced the water/nuts.

If your tapwater is 'hard' or has a lot of dissolved minerals, often limestone, this will cause the pH to rise. Nutrients also often include pH buffers, which will hold pH steady for a few days but will react with other things in tapwater and become less effective over the life of your tank of nute solution.

You can eliminate that problem by using distilled, RO or other demineralised water- or you can just live with the tapwater and just know it will need to be pH corrected.

[LOC NAR on probation]

I used hydrotron clay rocks in a drip system. You can keep washing them and use over and over. They handle the PH good and cheap too.

[Al B. Fuct]

LN, I started out with clay pellets in my flood op. Yes, they don't cause pH wandering and are cleanable (even sterilisable), but cleaning 23x 8" pots worth of the stuff totally free of old root material was a pain, so I switched to a disposable medium.

[Chabnoc]

HEY!!! thanks Al B. Fuct. You answered one of my next questions before I got to it. I have 8 plants growing in my Hydro system, and one in soil. I am praying the one in soil will be female, if so, this will be my mother for clones. These are Northern Light plants. and would like to keep this strain going if possible. very nice tutorial on cloning.

Thanks:thumbsup: