Frustrated w/ DWC + Lucas formula -- what is my issue?

Hi Liflow,

There are a lot of things to look at to try to figure out what's wrong with your grow. First, you didn't mention what type of lighting you have. That can be important when using the Lucas Formula. Also, if you're topping off with just pure R/O water, then you WILL need to change out your reservoir after you've added enough water to equal the original volume of your nute solution (5 gallons in your case). If you don't want to have change the res, then you need to use his add-back method. Look at the bottom half of the instructions on this post - http://forum.grasscity.com/advanced-growing-techniques/168243-lucas-formula.html to see how to figure out how to mix up the nute solution.

Second, are you foliar feeding the plants? Small yellow spots doesn't actually sound like cal/mag deficiency. Cal/mag usually produces rust color spots, if it's the spotting your getting. Can you post some pics? That would help a lot.

Third, the water clouding up sounds like your nutrient solution is destabilizing for some reason. Your suspicion about a bacteria *may* not be incorrect, but there could be other causes. The rising PPM suggests that something else is getting into your reservoir. Are your roots healthy? Are you having to adjust the pH at all, or is it staying stable? What growing medium are you using? Where did you get the buck, airstones, pumps, etc that you're using? Anything else that might be unusual about your set up?

 

Hmmm...it shouldn't be drifting up like that. The lucas formula is normally much more stable. R/O water is usually pretty much pH inert. You have to add a lot of it to move the pH very far.

Lots of bubbles are good. As long as everything was new then it's probably not some sort of contamination. Are you using hydrotron, or something else?

If you can figure out a way to take a peek without hurting the plant, I'd do so. Root rot is one of the things that will cause pH to shift upwards.

Otherwise, I'd double check the calibration of your pH meter and your TDS, just to be sure you're not having problems from faulty equipment.

Also, what are your res temps looking like?

 

Wow...I'm at a loss. Your temps are fine (65-70 is perfect, btw). Your medium is fine. Your pH is good, if less stable than it should be. In short, you're not making any of the normal mistakes that would cause problems.

Your PPM is spiking, though, which makes me think that *something* is getting into the reservoir and destabilizing your nutrient solution. You'll sometimes see the water turn cloudy like yours is doing if you add a lot of pH adjusters in, for example. But from the sound of it, you're not getting a chance to adjust the pH before the TDS goes wrong.

Is there any possible outside source of contamination? Is your secondary reservoir open to the air, by chance? Would it be possible to quit using the secondary res for a while, and maybe just use the drain tube and leave the main res sealed off?

Otherwise, I'm stumped. Maybe someone else has a suggestion?

P.S. DWC systems usually have a very good track record, in part because they're so very simple. A lot of growers have had good results from them. I'm guessing that there's something unique to your set up that's causing the problem.

 

Not that I am a hydro expert by any means, but when you balance your PH are you using proper PH up and down mixtures (and not vinegar/bicarb etc)?

Also, do you use both products in one mixing? (The reason I ask is that apparently you should try to only use one product at a time, if you add too much of either mixture and overshoot your desired PH you should dump your nutes and remix them, instead of using the opposite product to balance it out).


Also, I am assuming that you built your own DWC buckets? What sealant/glue did you use? Is it possible that some of it is breaking down and leeching into your nutes? What about the foil tape, is any of the adhesive sticky side touching the nutes? Hearing about the cloudy reservoir makes me think that something contaminating it for sure...

Good luck, and peace!

 

Good question. On the one hand, that stuff's designed to be used in household plumbing, so you'd think it should be pretty inert. On the other hand, raw nutrient solution is pretty acidic. Maybe it's possible it's dissolving the tape?

As for the algae, as long as your tubing is black, you shouldn't have any. Algae needs light, just like any other plant.

One other idea that occurred to me - test your pH and TDS of your R/O water before you add any nutes. Maybe something's wrong with the R/O system your using and your water isn't clean.

 

Damn, dude. Don't know what else to say .

It's pretty obvious that *something* is getting in your solution and messing it up, but I have no idea what.

 

i think your ph should be lower. Like 5.5-6.5....try to keep the pH lower in hydro setups..

 

Hey Liflow,

if your post above is not a type error, then you are burning your plants. 1340ppms @ .5 conversion is over 2.6EC. You should be under 2.0EC.

bring your ppms down under 1000 @ .5 conversion. Are you having to add PH up or down to your reservoir or topoffs?

Regards,
linedrivr

 

"What do I do? Dump my batch again? This is really getting old... I thought I could keep my nutes longer than a week..."

for what it is worth, I am 5 weeks into flowering now using a 4 bucket dwc system + 14 gal reservoir and have not had to dump/change my reservoir since I started this grow including veg time. I top off w/ pure RO all week and adjust nutes back up 1350 - 1400 (.7 conversion) on Saturdays. I dont have to add much micro and bloom to keep it at the 1300 - 1400 level (1000 or less in your case @ .5 conversion).

I have yet to need to add PH up or down. Mine stays between 5.4 - 6.1 all week. It climbs during the week while topping with PH 7.3 RO then drops when I feed micro/bloom on saturdays. Lucas claims that the PH swing from low 5's to low 6's is good for the plants to be able to uptake their needed nutrients.

with this being said, I have found that with the Lucas feeding schedule using GH micro/bloom, I have to add a pinch of epsom salts to the reservoir every couple weeks to keep from having magnesium def. I add 1ml per gallon in the system. I disolve it first in a gallon jug then pour into the reservoir. I have a magnetic driven water pump that re-circulates my nutes through the system and the magnet in it attracts my magnesium....lol

regards,
linedrivr

 

Interesting that you said this. With my current grow I've had to keep my nute solution at the very high limit of what my plants will tolerate or I get cal/mag deficiencies too. I'm currently running at about 1050ppm @ 0.5, which is actually stronger than what Lucas suggests, but that's what my girls seem to need.

Line, the problem is that he's using the 0-8-16 Lucas formula ratio, which is giving him 950ppm@0.5. The PPM then spikes to 1300+ for some reason and the nutes appear to be chealating (sp? lol). If he was starting out at 1340ppm, then I'd agree he was burning his plants, but that doesn't seem to be the case here.

 

true true.

I wonder if PH up or down is causing his ppms to rise. PH up will also cause your nutes to turn cloudy.

I had a mag def on my 1st grow and went to the site where Lucas still post and asked him why I was having the deficiency using full strength nutes. he told me I shouldnt be having one then I explained I had a full time re-circulating magnetic pump and he said that was causing my problem. He told me I could change out the pump or add a little epsom every now and then. The epsom cured my issue.

If PH up/down isnt causing the ppm spike, do we know what his reservoir temps are?

 

lol...your prob right. I just went with what was suggested. A little epsom cured my issues.

your issues are very puzzling.

Lucas is posting today. You could go over there and give him a brief rundown of your situation and see if he has an answer for you.

let me know if you need the site info and i will PM it to you.

Regards,
linedrivr