Hello guys and gals, Plants were started from seed one month ago today. They've been in 5gal bubble buckets for about 20 days now. For the last week I've been getting rusty looking spots on the lower leaves that progresses into the death of the entire affected leaf. The upper and new growth looks ok, though over the last couple of days, new growth has nearly stopped on 2 of them. Also, the two that are worse off have started to look a little droopy by the end of the lights off cycle, and perk back up when the lights come on. I have done a lot of research trying to figure this out, but I haven't been able to figure it out yet and they're looking bad at this point. Everything is kept very clean and sanitary, and is indoors, so I don't think it's a disease. I'm currently using RO water and GH 3 part, following their 3-2-1 schedule. Just changed nutes and raised EC from 0.8 to 1.3. That includes Cal/Mag at 5mg/Gal, and Hydroguard at 5ml/Gal. It's only been 14 hours, but I think the problem is accelerating with the new nute mixture. I'm really confused, because I thought I had finally pegged the problem as being a Mg deficiency. Ph has remained between 5.4 and 5.8 throughout the grow. My solution temps average around 23*c/74*f, but get up to as high as 27*c/80*f for for a few hours during the day. The roots look healthy to me. Air is provided to 4 five gallon buckets by a 20watt 670gph pump and 6" airstones. Lots of bubbles. Light is 1000w MH, air cooled, about 20" above the top of the plants. Air temps stay between 23 and 28*c. Lots of airflow in the tent and no recycled air. Old air vents outside of the room and new air enters the tent through a passive intake. I'm praying like hell that one of you can tell me what I'm doing wrong. I just want these girls to be happy again. Thanks!
At those solution temps, I am surprised you can't smell root rot symptoms. I recommend you get the temp below 70deg F.
Couple things... I feel your air pump would be good for 2 of those 5 gallon buckets. For dwc you want pumps that come rated in liters per minute or a really high gph The pump you've got is effectively only 11 liters per minute. If you were to follow 2 liters of air per minute to every gallon of water you are way below the minimum. I run a 70 lpm 60w pump for 25 gallons of water. The pump may have been fine when the plants root mass was smaller. As it gets bigger its going to take up more space and use more o2 in the water. When it comes to dwc you want to be excessive with the amount of air you're pumping into the buckets. I've also got a 5g and a 3g bucket hooked up to another 8 port 70 lpm pump. They are basically each getting 35 liters of air per minute in each bucket. Totally extreme. Being extreme with your air in the reservoirs is one of the best tools in our book to ward of root rot. Also the colder water is the more oxygen it can hold. As it warms up it holds less and less. Combine this with a weak pump and you're asking for disaster. Your ph floating between 5.4 and 5.8 is way to low. For dwc you want to maintain your ph between 5.8 and 6.2 How are you adding your nutrients into the buckets? Do you do micro first then bloom and grow? With the gh 3 part you have to use micro first. They are looking droopy as the day goes on because ots getting warmer and your water is holding less oxygen. They look perky in the morning because the solution is cooler and holding more oxygen. Address the amount of air being pumped into the buckets and you will most likely see improvement. Change your ph to a value more suitable for dwc 5.8 to 6.2 and you should see the spots stop appearing. Do you have a ppm meter? This would check the total amount of dissolved solids inside the reservoir. I'm wondering how hot (ppm value) the solution is. What do the very end of the leaf tips look like? Are they yellowing up? That's all I got at the moment.
Thanks for the quick replies. I thought my air pump was adequate, this really changes my perspective on that. And it's even more critical since my res temps are above the "ideal" mark. I'll probably add a chiller and convert to recirculating eventually, but for now I'm doing the best I can with the temps. I'll order another air pump and dedicate one to each pair of buckets, and I'll raise the ph immediately. I do add the micro first, then give it a quick stir before adding the other nutes. Yes, I have a ppm meter. EC is around 1.3 which should be 650 to 700 ppm if you use the .5 conversion. I'll have a look at the tips when the lights are back on. They never looked burnt before, but I just bumped the nute strength with last night's res change, so we'll see. Thanks again.
For reference, this is the pump I'm using now...http://www.amazon.com/Commercial-20watts-120volt-Hydroponics-Aquarium/dp/B00BVLBNB2 Would this pump be going too overboard? https://www.1000bulbs.com/product/110873/GROW-746510.html Again, I'm running four 5 gallon buckets.
Yeah the pump you're using is about 37 lpm. If you divide that airflow between your 4 buckets its really pushing it on the bare minimum side That pump in the 2nd link would be better. It's similar to the one I use but man its pricey. From experience with the 70 lpm pump it works great with 4 buckets. If you try to add a fifth it will work but everything kinda suffers. I wonder how quiet it really is... Here's the one I use. I have 2 of them and the noise of the bubbles is louder than the pump running. http://www.amazon.com/Hydrofarm-AAPA70L-60-Watt-Commercial-Outlets/dp/B002JPM91W Iirc they are $50 a pop.
Damn that price is much easier to swallow. I'll give that one a try. I can't believe it's that quiet though. The pump I'm using now is crazy loud. Hopefully this helps. Unless I'm overfeeding them or the water is just too hot, I can't think of anything else to address.
Cheers! Raise your ph levels as well. You want to be in the 5.8 to 6.2 range specifically for dwc applications.
Update: pH levels have remained at around 6 for the last 2 weeks, and the plants now have a chilled RDWC setup to call their home. The new air pump is rated at 70lpm, which should be bordering on overkill for 15 gallons of soup. Water temp hovers right around 20* celsius now. The plants are growing like a wildfire, but they still get the same brown-ish spots on older growth. Also, some of the leaf tips are curling downward a bit. EC has been maintained at 0.9 to 1.0 for the last couple of weeks. Still using GH 3-part on the 3-2-1 schedule and Cal-Mag at 1/4 strength. Any other ideas? Could it be nute burn? Something wrong with the nutes? Something weird with the strain? Thanks guys.