Root riot cubes are amazing and much better than rock wool! They are like a sponge so if they are soaked entirely, they still have air since they are porous. I run 900-1000 EC early veg first week or so, and bump it up to 1200 EC and seeing how the plant responds. Check it at least once a day. If it drops down from 1200, bump it up to 1300 or 1400. If it leaches up from 1200 to 1300, drop it down to 1100 or 1000 EC. Every plant and strain reacts differently, gotta find the sweet spot. Make sure the ph stays between 5.8 and 6.2 let it swing around that general area, dont be strict with a specific number as it will get full adavantage of nutrient uptake within the high and low side of that ph range.