Rockwool, How wet is too wet?

I have a flood table containing 4" cubes. I was originally under the impression it was impossible to over water rockwool but 5 cycles a day seems to much. My question is, how many cycles/day is average for 80 deg space, OR how can I tell when a cube is too dry/too wet so I can adjust my flood cycles accordingly. Love the site, amazing community!

Bump, anyone?? Need some advice soon before I lose my crop

You probably don't need to flood them that often. I only water my 4" rockwool every three days at the most. If the plants are big enough to need more then that then you might want to transplant them into something bigger. Also if you have hyrdroton or something in your table just lift the cubes a little above the flood line and let the roots just go into the hydroton. That's how it is usually set up because rockwool does actually hold to much moisture for a little bit if it gets soaked, so by the time you need to water the rockwool again the hydroton has been dry for a few days.

Someguy15 said:

Bump, anyone?? Need some advice soon before I lose my crop

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I was having some fairly seriously issues with my plants in rockwool, most of which could be attributed to over watering. I also was under the impression that rockwool couldn't be over watered (as per posts on this forum) and had my plants set to be watered every 3 hours for 15 minutes (8 times a day).

Once I realized how badly I was over watering, I turned the water off completely for a few days to let the cubes dry. The 4" cubes stayed WET for nearly three days. On day four, the cubes felt slightly moist but light enough when I lifted them to be considered dry.

I manually watered them today and am documenting how long it takes for them to "dry". At that point I'll have a good estimate of how often I need to water. From what I can see so far, 5 minutes of watering every 12-24 hours or so should be more than enough, depending on how much your plants are drinking.

Also, I spoke with a rep from Advanced Nutrients who gave me a bit of an experiment to run. He advised me to watch the cubes to see how long they take to dry, which would tell me how quickly they're drinking.

Dry in 7-9 days: Over watering (duh)
Dry in 1-3 days: Proper
Dry between waterings: Under watering

Hope I helped in some way.

Im having the same problem with my set up! The thing that worries is the roots. They are just sitting in the hydroton while I wait for my cubes to dry enough to water. Right now I'm watering once a day. Doesn't seem like enough

i recently setup a grow tent for a friend,

erected tent, hung lights, fitted fans, carbon filter,

put in a 8 plant nft systen layed spreader mat

then some clones into the nft - they were in 4 inch rockwool cubes,

i set the nft to water for 15 mins, every hour,

she just harvested a few days ago an they seemed to be nice plants,

about 2 oz minimum per plant,

now ive spoken to her about this watering scenario,

i hand watered a crop from start to harvest last year,

i had them sitting in 2 rockwool cubes taped to each over, so they were growing in rw 4 x 4 wide and 8 inches deep

watred them every 3 - 4 hours during veg and every 2-3 hours during flower.... they grew 5 - 6 feet each,
they were monsters,

and yeilded 3- 4 oz a plant

im going to do some the same way this year but in 4 x 4 in rockwool cubes ontop of each over

they gonna be massive !!

ill post the grow on this thread as its kinda the same subject,

personally its easyer to water using a nft on a timer,

but manual watering lets u learn about the plants better

Thanks for the tips, I'll back it off to two floods/day and see how close to dry they are before the following flood. From what I'm hearing 1x a day might even be sufficient while they are this small.


(foil has been replaced with white plastic)

1 time a day is all you need with a small plant, maybe 2 when they get bigger

You really only need less than 1/4 cup to dampen the 4" cubes. You can take the plastic off the cubes to dry faster but once dry only use fresh water for a bit because the water evaporates but the nutes stay. If you don't use fresh water you will get nute burn.