i think ebb and flow is definitely your best bet for that number of plants.

the water should wet the rockwool. If you let the water sit for a few minutes the rockwool will wick the water up, so you probably don't have to let the water get that high (though i bet you can if you want).

evaporation: i guess just keep adding more water, or put a cover over your tray.

rockwool: i'm pretty sure this is all you need, though make sure you don't soak it too much. rockwool holds more water than most hydroponic media, so you can ebb and flow less often
Cornelius Reviewed by Cornelius on . EBB and FLOW with rockwool Hi guys, I need some help. I'm growing in a 2' x 4' planter with drainage at the two opposite ends lengthwise. I currently have 15 plants in a mix of 4" and 4" x 4" x 2.5" rockwool blocks, with a flat of seedlings under a tent. I am planning to increase to at least 40 plants, with a soft cap probably around 65. I am toying with the notion of putting these plants onto rockwool slabs. I would like to stay with rockwool, as this allows me to remove only the ones I want flower. I have very Rating: 5