How Often to Ebb and Flow Rockwool Cubes?

Been growing a long time via other methods but entirely new to rockwool and fairly new to ebb and flow, and could use some basic watering theory if you rockwool pro's would be so good to me.

I'm trying an ebb and flow system with 4x4x4 rockwool cubes. I've received already established plants in 3x3x2.5 rockwool cubes that I was planning to place on top of the 4x4x4 cubes. So....will flooding the 4x4x4's wick up enough water for the 3x3x2.5's on top? Or do I flood all the way up to the 3's? Or just the bottom of the 4's? And how often? Should rockwool stay wet and heavy, or actually get light? I've googled it a bit but not found really consistent info...

Thanks!

The has been discussed recently on here. I believe in the last thread the post that was most liked said he floods 4 times a day.
I do I all my veg in rockwool so from seed/clone to small plant. My magic number is like he said 3-4, but you may use more in heavy bloom perhaps?

Also that thread said most ppl have better results just flooding a few inches up the cube for best results.
Hope that helped.

I flood every 2 hours dont know if its right but it works

Rockwool as a medium holds moisture very well. My last grow I flooded my rockwool slabs once a day until about the 3rd week in and then increased with another flooding time. 15 minutes @ sunrise (or lights on). During flowering I only needed to water once a day and was fine.

Flooding the 4x4's (a couple of inches up) should wick up the water to your smaller RW cubes on top but it's best to double check after a trial flood. If your top slabs are well flush against the bottom slabs then you should be good.

RW should initially be wet and heavy (but not fully saturated/soaked!) when you first flood but by the end of the day the slabs shouldn't be "wet" feeling but rather mildly damp. If your RW feels too dry near lights off then increase your feeding.

Thanks. My plants are only about 6" tall and wide, and the cubes are still heavy 24 hrs after flooding, it would probably take a few days to actually become light. I was wondering if it was better to give them regular flooding even if not drying out but perhaps that would drown them? Can a well drained rockwool cube still be too wet and droop a plant from too frequent waterings?

I would not fully flood up to the 1st set of cubes, just flooding til the 4x4 cubes are wet will be enough. That will wick, and eventually the roots will grow down into it. Letting it wick a bit instead of it getting full soaked will provide it with a good oxygen to water ratio.

When I used just clay pebbles I flooded 4x a day. I came onto making a nice mix of rock wool pieces and clay, found it better to water 2x a day, lights on and prior to lights off. All my waterings are 15 minutes, you might need longer, pending on how big your tables are. In that 15m my flood table gets max cap and holds it for 5 minutes or so before drainage, then drainage is about 8 minutes it self.
This is all personal opinion and personal experience. Good luck.

poindexterous said:

Thanks. My plants are only about 6" tall and wide, and the cubes are still heavy 24 hrs after flooding, it would probably take a few days to actually become light. I was wondering if it was better to give them regular flooding even if not drying out but perhaps that would drown them? Can a well drained rockwool cube still be too wet and droop a plant from too frequent waterings?

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Rockwool retains ALOT of water, which is why I recommend when you xfer them to the 4x4 cubes, Just let the 4x4's get soaked and if it wicks a bit that will be enough. Doing this will allow a good ratio of water/oxygen at the root mass.

Thanks for the perspective. Sounds like a daily 2" deep flood will be more than enough then, at least till they get bigger. I've got 16 plants in a 4x4 pattern in a 30" square tray under a 400mh. Half the plants look perky and psyched, and the other half a little droopy, maybe too wet? Hoping restraint on the watering will bring them back...