DeltaEye

@gottagrowsometime, I never said the rockwool would keep pH 4,5, which indeed would be over 30x more acidic (or 4 100x acidic) than it should be. Still, I've never heard of anyone even soaking or "treating" their rockwool in such acidic water intentionally so I was just curious and you mentioned having pH issues. But I'm glad you got it! Lol.

@gottagrowsometime, Okay, I'm guessing you checked the pH of the water after you had soaked the rockwool cubes in or the runoff from the cubes. pH 4.5 just sounds really acidic to me to start with, maybe if your rockwool is really alkaline (like 9 sounds like...) and you were soaking it in a small volume of water.. I just measured the pH of 20L of water that I had adjusted to around pH 6 before adding twenty Grodan 7,5cm x 7,5cm cubes (1 liter of pH 6 water per cube) in and been letting them soak for a week. The pH had only risen to 6.7-6.8.

Looking good! Way ahead of mine at this point.😅