Overwatering

[Atulip]

Problem: Droopy leaves

Medium/grow method: 2" rockwool cubes in an expanded clay table

Feed: and supplements used: GH trio + calimagic, 600ppm total, pH drifts up to 6.5, pH'd down to 5.8 each day.

water source: RO

Strain/age: SoFem Cloud Candy photoperiod, 3 weeks from cut.

light used: 3500k Cobs and a mars sp3000

Climate: 80°F, 45% RH

Additional info: Ebb and flow flooded every 5 hours while lights are on. 18/6 lighting, 4 floods a day. Flood level is the lowest, about 2 inches. Leaves are not dry or brittle, cube feels moist, but the roots should be in the pebbles now. They've been on the flood table for 8 days now and the droopiness started a few days ago.

 

[Mañ'O'Green]

If your flood trays are not draining completely and the rock wool cubes are in contact with the table they will wick too much water up into the cube and the roots will not get enough air. You may get some crown rot? Are you running HydroGuard? Are you aerating the reservoir? You should not flood until two hours after lights on and two hours before lights out.

You need to double check that humidity sensor. RH would normally run high with that set-up?

PH is too high on the top end 5.7 - 6.2. You seem to be getting a lot of PH drift for RO water? Did you buy PH balanced Hydroton? If you bought the inexpensive clay pebbles you will not solve this problem. 3 inches of stones is not enough for the number of plants you have in there.

 

[Mañ'O'Green]

I just thought of something else what is the volume of your reservoir and how much PH down do you use between reservoir changes? If you are using Phosphoric Acid as PH down the result is elevated Phosphorus when you need more nitrogen and less phosphorus. So you should be using Nitric Acid in the veg state. This will increase the nitrogen levels. That said there are still limits to the amount of either that can be added before the nutrient balance in the reservoir gets so out of balance it creates lock-outs. This goes back to the pebbles question again.

 

[Atulip]

If your flood trays are not draining completely and the rock wool cubes are in contact with the table they will wick too much water up into the cube and the roots will not get enough air. You may get some crown rot? Are you running HydroGuard? Are you aerating the reservoir? You should not flood until two hours after lights on and two hours before lights out.

You need to double check that humidity sensor. RH would normally run high with that set-up?

PH is too high on the top end 5.7 - 6.2. You seem to be getting a lot of PH drift for RO water? Did you buy PH balanced Hydroton? If you bought the inexpensive clay pebbles you will not solve this problem. 3 inches of stones is not enough for the number of plants you have in there.

The flood tables are draining fully, and the small cubes are on a layer of pebbles above the bottom still. I am using hydroguard, but I am not aerating the reservoir. Flooding is about 1.5hours after lights on, and the same before lights out. The top hydroton never gets wet, so I assumed that's why the humidity is still low.

No idea if the hydroton was pH balanced but it was "for hydroponics". It was washed twice and then again with 5.5pH water before the grow started. I do leave the RO exposed to air, it's 6.8pH currently. When I keep it enclosed the pH goes as low as 5.5.

I just thought of something else what is the volume of your reservoir and how much PH down do you use between reservoir changes? If you are using Phosphoric Acid as PH down the result is elevated Phosphorus when you need more nitrogen and less phosphorus. So you should be using Nitric Acid in the veg state. This will increase the nitrogen levels. That said there are still limits to the amount of either that can be added before the nutrient balance in the reservoir gets so out of balance it creates lock-outs. This goes back to the pebbles question again.

27 gallons with about 12 gallons in it currently. And quite a bit of pH down is needed, 50-75 drops each day, around 3mL. It's GH down and it looks like its only phosphoric acid.


Res change was scheduled for tomorrow but I'll do it today and look for a different pH down. pH has drifted back up to 6.4 already.

 

[Atulip]

Any recommendations for nitric acid pH down? Everything I'm finding is phosphoric or sulfuric.

 

[Mañ'O'Green]

Take a gallon of those clay pebbles and put PH 5.8 RO or distilled water on them overnight and see if the PH changes.

 

[Atulip]

Looks like they've perked up a bit since a res change. And I dumped some hydroton in 5.5pH water this morning and it's 6.5 tonight so that's the culprit.