I have a plant in a 4" rockwool block, started out in a little clone cube and I put it into the hole in the big block. Roots have grown through the block and out the bottom nicely, but I'm worried about the rockwool staying wet (it's ebb & flow). If I flooded it only when the rockwool dried out a bit, it would flood about every few days....I have some blocks that I presoaked that are still kinda damp, and have been sitting on a shelf for a week I know it doesn't have to dry out, but is the block staying wet going to drown the roots in the block? I have an air pump oxygenating the reservoir, and the fill line has holes cut into it to reduce flow (396gph pump is too much) that agitate the water a bunch when it's filling, could this provide enough oxygenated water to be able to flood every few hours, or is the block still supposed to dry out? I'm currently flooding whenever the hydroton is mostly dry where the roots are under the block (or at that level next to it). The roots are growing really damn fast out of the bottom and the new growth looks good, I'm just making sure I got it all down before my batch of clones is ready to be transplanted into the ebb & flow.
One flooding of oxygenated water per day will be ideal for 4" cubes, depending on humidity, it should be high for clones. An air stone/curtain in the reservior is a must with all hydro systems, yes it oxygenates the water/solution, but it also keeps the solution fresh and circulating. You can set the timer for any time during 24/7 light cycle, if you have a dark period, set your timer to flood an hour or so after lights on. Plants feed during lights on, that gives them time to use up the water/nutrients, and not have them lying in the rockwool during lights off.