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Need help to indentify these symptoms/deficiency


Topic starter

Hello again to this community! 

If anyone could help me to indentify these symptoms and maybe help thru how to fix that. would be more than super! 

So this is my first DWC grow. Ive only soil cultivations under the belt. So this was one for me, but I had the basic idea and understanding pH and EC/ppm values. 
Little background info: using 4 gallon reservoir and 252l/h adjustable air pump. So everything with oxygenation should be ok. 
The strain Im growing in DWC is Critical 2.0 XL autoflower. (Idk if anything could be this much strain related?) 

Nutrients Im using is GHE aka nowdays Terra Aquatica TriPart-series Micro(soft water), Grow & Bloom. Also having GHE’s Silicate and BioBizz Cal removed link  

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started the seedling in RW cube and shortly after 2-3 days transplanted it into DWC net cup. The troubles basicly started as soon as started to top feed before the roots hit the water. 

And first of all it looked like a Potassium deficiency, but I guss it wasn’t and now only two options I can come up with is Calcium deficiency or Fungus gnats.. 

This is how the plant is currently looking. The first actual real 5 finger leaves being almost dead. Serrated leaves and three fingers died like a week ago. She is 20 days old now. 
(Cant get the images uploaded on thread, so srry for link images)
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These match with Calcium deficiency, but the thing is theres 0.7ml/l Cal/Mag mixed in the reservoir and pH being adjusted twice per day to 5.8. In like 12hrs pH usually climbs up to 6.2-6.4 then I reset it back to 5.7 or 5.8

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But if this is a Calcium deficiency why does it keeps appearing and getting worse time to time? 
As mentioned there should be plenty of Calcium available from Micro, Cal/Mag and Silicate. 

and this is it two days ago. If u look above you can see its rapidly spreading now. 
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The new shoots also being discoloured/yellowish and brown.

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Calcium should absorb at least from 6pH so idk if the absorbtion can be the problem(?) 

And the roots looking OK to me. Theres some brown just below the net cup, but Ive been told that GHE’s Micro does that tint.. 

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Ive tried to flush the net cup also couple of times with pH’d water and one time there was a silicate mixed a bit and once 6.0pH water and Cal/Mag with low dose. 

Im actually so lost with this and feels like Ive tried to search for everything but can’t find a way to fix it. 
If anybody could take a depth look with me, I would appreciate that much! 

Also probably forgot to mention something so don’t hesitate to ask for more info!

If it matters using mars hydro ts1000 LED and for the DWC water using tap water (very soft water here) Water EC is close to 0.2 and pH is 8.2

Tent temp is fine between 23-25C, DWC water temp is steady 21C, RH is ~35-45% and fresh air is intaken from outside. So the environments should be close to perfect. 

3 Answers

Hey there @lilvexed. Congrats on your DWC system, sorry it's working against you atm. You gave a lot of info, but I'm missing the EC of the solution that the plant is in.

So your problem is more than likely related to the rockwool and Hydoton clay pebbles. They both need to be buffered before use. Meaning, that they should be soak before using, in Ph'ed water 5.8 with beneficial bacteria. But what's done is done. So move on is all you can do with auto's.

So you have some bad shit in the net pot, and that's what some of the problem is. So you need to rinse the net pot everyday for four days min, five days won't hurt. Prepare the water, add twice as much beneficial bacteria as called for. Then PH to 5.8. Pour 1L over the top of the pebbles and rinse the shit out of it. Then I let it sit in it for 10-15 mins, submerged. While this is happening, you'll dump out the container that it's in, and wash with soap and water. Wipe it dry. Fill with fresh nutrients, Ph'ed to 5.8. Make sure the water level is 1"/25mm below the net pot. You will need to repeat the rinse everyday for the four or five days. This will correct the buffer problem and the slime problem. You should rinse the hydroton every time you change the rez to keep it inoculated. I pour the solution over my hydroton before I change the rez. It rinses everything, then gets dumped. Check your meter and make sure you know how to calibrate it. If you need help, shout out.

My net pot fit snugly, find something like this. Fill it to the top and let them sit, 10-15 mins.

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Here's some info that might help. These good number to try and obtain. Your RH needs to be up around 70%, yours is way too low. Get it up man. 🤣 

Cover your hydroton with something to block the light, this is where the other part of your problem is coming from. Light will get through and make problems. No light, cover tops of net pots and top of container it's self too.

I'm on the west side of the pond so that's my schedule. I hope this helps you man. Just keep talking and you'll get through this grow. 👍               peace


The problem remains and got some more info/knowledge…


So first of all I realized that there was like 14ppm Fe in my res mix. Thats way too much when the recommendation is like 3ppm.. That much Fe came from Silicate and GHE FloraMicro.

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And by watching this mulders chart, if theres excess Fe it affects at least on Ca and K uptake….Or causes a lockout. 

And by looking the plant you can clearly tell theres hard Calcium deficiency going on. And not only a deficiency. There is something still blocking Ca uptake, since it keeps getting worse. There is ~150ppm (1.2ml/l) of Cal/Mag available in res but plant wont absorb it.

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Ive reduced the Fe amount down to 1.5ppm (did a res change and ditched the silica)

But it wont absorb Ca… I don’t know what still could cause Calcium to lockout? Anyone?? 

Posted by: @woodi2

but I'm missing the EC of the solution that the plant is in

Tried many different EC values. Right now it is high as 1.7. She drinks and eats (.1 EC drop per 24h) 

that is pretty high value, but it looks like shes fine with it. No any kind of nutrient burn. 

Posted by: @woodi2


So your problem is more than likely related to the rockwool and Hydoton clay pebbles. They both need to be buffered before use. Meaning, that they should be soak before using, in Ph'ed water 5.8 with beneficial bacteria. But what's done is done. So move on is all you can do with auto's.

I don’t think so. Hydroton were flushed/rinsed with tap water (not pH’d) but RW were buffered to 5.8 from the start.

I don’t think theres anything shit in my net cup anymore. Since Ive flushed it multiple times also already. 
First time when I suspected fungus gnats (didn’t have Hydroguard by then) I flushed the basket first with ph’d water + Silicate mix. And after realized there was excess Fe and still suspected gnats I flushed the net cup with 3% hydrogen peroxide (1 part 5) 

So peroxide kills alll the bacteria and shit from the medium, and should have cleared the Silica remains (if there was in hydroton) 

After peroxide flush I started to use Botnicares Hydroguard. Which contains BT Bacillus bacteria, which is basicly the best bacteria for cannabis plant roots. And bacillus should also take care if theres fungus gnats..

So I flushed the net cup twice with ph’d water where was 1ml/l (2x higher than recommended) Hydroguard mixed. And obv I added Hydroguard to the reservoir. Theyve had Hydroguard for ~3-4 days. So the good bacteria should start forming…But still Ca is locking out. 

Posted by: @woodi2

Your RH needs to be up around 70%, yours is way too low. Get it up man.

Upping the humidity does not solve the problem unfortunately. If its written all over the internet veg humidity should be between 40-70%, thats just general info. And sorry not trying to be rude or nothing, dont get me wrong. But only if I would want to make changes on my VPD, then I only would want to take actions with humidity. My VPD being off like +2… and best for veg would be like 1.2 tops. I would have to take actions with my temps (would have to reduce the temperature and rise humidity to achieve lower VPD) But only way to lower the temp is raise the lamp, but then again plants wont get that much light so VPD is not on the point. Ive done very well before from seedling to harvest between 30-40% RH. 

And yeah Ive hydroton covered now. 
but the roots are okay. They feel kinda like ”coarse” not slimy at all. They do not smell. Was surprised how they do not smell at all. I just can’t belive it could be root rot. So let’s leave that out. I have a good hunch about it. 

TLDR; There could be something still causing Ca and maybe K to lockout, which causing major Calcium deficiency. 
What could cause it still to lockout? Is there anything that I just don’t get how I could fix that? 


0.7ml/l should be plenty for this stage and I've never had a CalMag deficiency shrivel up the plant like that. I'd take a closer look at your roots. Are they slimy at all? Bad smell? Any possible light leaks getting into the water? Are you using hydroguard or any other type of beneficial bacteria? There are a couple of us hydro guys here. I'm sure @woodi2 will be by soon to help out.

Topic starter

Couldn’t fit all the images there, so heres how the roots looking:

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And this is how to the new shoots looks like:

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Hey man, wow lots of info. Well here my 2 cents. Your roots look bad from the pic above. If you would do the rinse for the 4 days, and clean and scrub your bucket. Replace the nutrients to 1.1-1.2 EC, with all the recommended amounts of each. If your running a EC of 1.7, that is too high for your plants. They should be around 1.0 EC or lower. If your feeding is erratic, then the plant is to and will take time to recover. Keeping it simple is the best way to get the best results. But that is what I'd do, flush for four days. Reduce EC to 1.0 with correct portions for the four day. Clean their environment, and triple check for any light leaks. That's what I call resetting them. This is what works for me. I try not to make it more complicated, I'm confused enough my friend. 😉  I hope this helps.

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