Here ya go.. should answer your question.
ripped from
Grodan's website:
Grodan Stonewool is pH Neutral!
It is a common misunderstanding that
Grodan is alkaline and that one has to continuously adjust the pH, when in fact Stonewool is pH neutral.
The confusion stems from the fact that
Grodan has some residual lime from production. Follow this simple procedure to remove this un-buffered lime. Begin by saturating the stonewool in pH 5.5 water ½ hour before use. There will be a rise in pH of about 1.0 from the residual lime dissolving. The final step involves flushing the "dissolved Lime" from the stonewool with your nutrient solution just prior to planting or sowing. From this point onwards, the pH neutral
Grodan Stonewool will not contribute to any changes in the pH of the solution.
Note: Ensuring pH values remain between values 5.5 – 6.5 is essential for optimum plant development and optimum substrate integrity. If you condition
Grodan products with a solution pH lower than 5.0, you risk damaging the Stonewool, so take steps to ensure values do not go below pH 5.0
Why does pH change ?
When the plant grows the pH goes up because of the root activity involved in nutrient uptake of the plant. If the pH is not going up, your plant is not actively growing!
When the plant gets ready to set flowers or fruit, the pH will briefly drop. So when you notice this drop, the plant is signaling that it is time to change to your bloom-solution.
So in answer to your questions; You should always stay above pH 5.0 (better to use pH 5.5), because
Grodan begins to dissolve below pH 5. You can soak the cubes on your table. You don't need to cycle, as long as the cubes are soaked initially. However, you do need to add the final step of watering from the top in order to flush out the lime residue. You should also get rid of the drained water, as it contains the lime residue.