,@Catfish22, So far, so good. I started the seeds this way, instead of placing the seeds directly into the rock wool cubes, not knowing whether they sprouted or not, I can see which are viable and then carefully place them into the cubes. I've been doing it this way for the last nine grows now. The pH of 5.0 was recommended by a dealer (of hydro supplies) whom I bought my first Bubble Phonics system from.