pH in rockwool going ham

Hey guys, I'm currently growing in 6 inch grodan rockwool cubes, watering by hand.

I started them properly by soaking them in ph 5.2 water for an hour. then i flushed them with 1/2 str nutrient solution pH'd at 5.8

Transplanted my babies and everything was fine for like 2 weeks, then they started curling and twisting, so i checked the runoff ph and it is 7.5......... WAT.

So now I'm basically flushing them every day because i am checking the runoff and it is rising to 7+ every day. What do I do? can i just ph the nutrient solution lower (like 5.5) to offset the extreme drift????

I don't care what Grodan says, they need to be soaked for 24 hours. Especially when using such large blocks. If you are doing drain to waste, a pH of 5.5 should be fine.

What nutes you using?

Blue planet nutrients. their farmers pride organic line.

From what I gather and have read rockwool is brutal on raising the pH. I've only used it for small cubes for clones (when I run out of rapid rooters) so haven't had any serious problems with it. But if you google "rockwool raise pH" you'll find lots of other growers having the same problems with it as you are. Good luck finding a solution!

I alway soaked my medium in 5.5 water also precharged to 400ppm of base nutes.
for best results

I am aware of the pH spikes associated with rockwool. just didn't soak them long enough, I guess.

I have literally flushed these 2 blocks with 3 GALLONS EACH pH 5.5 water and the runoff is STILL not going under 6.5. WHAT THE HECK, GRODAN? i want my money back >.>

DynamiteBob said:

I am aware of the pH spikes associated with rockwool. just didn't soak them long enough, I guess.

I have literally flushed these 2 blocks with 3 GALLONS EACH pH 5.5 water and the runoff is STILL not going under 6.5. WHAT THE HECK, GRODAN? i want my money back >.>

Click to expand...

Before you throw grodan to the trash! How do the plants look? I cant tell you how many bags of this shit i have
used in my lifetime but its lots.. Never had a issue but never paid to much attention to run of neither

Nutrient availability looks ok but leaves are twisting quite a bit.