Advice needed nutrient strength

Hi guys and gals
Ok so I’m growing 4 different strains in a rdwc (I know silly me) the new growth seems to be wilting almost folding up on 2 of the plants they all lack overall vigour.
Using gh maxi series.
2 weeks into 12/12
Ppm was 750 with ph 6.1
I topped up with plain water 2 days ago
Ppm dropped to 600 ph 5.7
I’m not sure if I’ve over done it with nutrient strength or underdone. I seem to get one plant going good just to watch another one start to fail. Any ideas what would cause this I’m sure its nutrient related maybe too much nitrogen they do look a bit dark green. Any tips on how to bring them back to life or should I start again with 4 similar strains and not waste my time continuing as it seems to be a rob peter to pay paul situation.

I’m not a hydro guy but I think @Myfriendis410 is. Wait till he wakes, he should be able to help

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What are you using to calibrate PPM and pH, I use a top of the line Myron-L and chemical test pH with bromothymol blue. Just by looks alone I would water down the batch by at least 10% to be safe. How often you “flush” is also important to remove residual salts.


What is the distance between your net pots and water level in buckets? And water temps? I don’t really see anything in those pics screaming that you have a nutrient issue. 600ppm seems a little low, and make sure to keep your ph close too. Hopefully some of the hydro guys will be by soon.

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They are fine, no need to start over, you’d be surprised what they can come back from. I’m around the same time with mine, I use the Flora series though. PH needs a bit lower. I’m running 5.7 at 950~TDS.

I run 50% of the manufacturer’s recommended dose and don’t have any issues.

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Here’s what I’ve learned in hydro and what to watch for:

Water temps need to be under 70F. Running something like Hydroguard (bacteria) is helpful to cut down on root rot.

Water level needs to be 1 to 2 inched below net pot. Aeration should be continuous and vigorous (rolling boil).

How do the roots look? Smell? If slimy or smelly (or both) then root rot (pythium) has set in.

Also: plants start to anticipate lights out and lights on by changing their posture. The pictures kinda look like sleepy plants.

A TDS of 750 is fine for veg but light for flower. The ruling thinking is between 1,200 and 1,400 in mid flower but you are finding out the problem with the “R” in RDWC: you can’t adjust for individual plants. I’m dealing with that now.

PH is a bit high: I like 5.8-5.9.

If they are starting flower then flowering nutes need to be introduced. I use the Lucas formula (GH Micro/Bloom in a 1/2 ratio) plus Liquid Kool Bloom. My target TDS in week 6 of flower is 1,100 ppm.

Overall, plants look pretty good.

Here’s the hydro guys: @TDubWilly, @Bogleg, @kabongster


All the environmental factors need to be considered too.

What is your temp range and humidity range? Day time and night time?

Everything @myfriendis410 said I second. My general rule of thumb for PPM ranges is:

Seedling - 200ppm
Early veg - 400ppm
Mid veg - 600ppm
Late veg - 800ppm
Early flower - 1000ppm
Mid-to-late flower - 1200ppm


I’m using a bluelab ph pen and a cheap ppm pen (I like it as it measures increments of 1ppm) so you can tell what’s happening daily instead of the truncheon which measure increments of 50-100ppm
My rh sits around 70% I have no way to bring down I’m stuck with whatever the weather brings my way. I have a small dehumidifier in the same room as tent but it cant keep up with the extraction fans pulling in more humid air than it can handle so just wasting power really.

I’ve just had a look at the roots and it seems I have slime building up in the air gap between water level and net pot. Im assuming this area is perfect for growing root rot(which is weird because I run a chiller at 21C and my air pump is more than sufficient)i have been running the water level a little bit low maybe 2 inches from net pot. I’ve previously added some h202 to combat what I thought was algae building up on pumps and it cleaned the buckets up almost over night hence the white bottom half of root ball. Theres no light leaks. I’m guessing I just didnt clean well enough last run. What are my options increase water level to cover the slime and add some h202 to try to kill it.

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slime and root rot are resilient…you can fight them but once in place they are nearly impossible to get rid of.

I have been advised to raise the water level to the bucket rim, add 3% hydrogen peroxide at 30 ml/gallon and let the roots sit in this with the air pump running for and hour, drain and fill the bucket to the normal depth inches below the net pot with 3% hydrogen peroxide added at 15 ml/gallon daily…you may need to add hydrogen peroxide for the rest of the grow…or with a fresh reservoir, add beneficial bacteria, enzymes and mycorrizhae to fight and replace the bad stuff and get rid of the rotten roots…no matter which choice you make, it’ll be a fight to the end…from my experiences.

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Happy Birthday @kabongster :grin:

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Thank you @Missiles! :blush:

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Interesting. I see a lot of moisture on your hydroton. How big of an air gap are you maintaining? I have gotten root rot on two plants (both at the same time, both in the same style of reservoir - in both cases in an 8 gallon tote with just one 2" air stone), but on both occasions it happened below the water surface - the roots in the air gap remained white and healthy.

In fact, I ended up cutting all the roots off that were below the water line on both the plants that had the issue (they were in veg still). One was an auto and one was a photo - they both recovered and yielded nicely.

Have you considered going the other way, and instead of trying to kill it all off with H2O2, introducing beneficial microbes - for example with something like Hydroguard?

My remedy for the issue was to add another air stone to each of my buckets and start using Hydroguard throughout my grows - I haven’t had any issues since. I try to use a 2" air stone for every 4-5 gallons of water in my reservoir.

Oxygen is your friend here.


In that photo the air gap was over 2 inches.
I have a micro pore ring from current culture for air distribution and as you can see in the pic there seems to be plenty of bubbles hence the wet hydroton. I cant get hydroguard in without paying massive freight charges.
I’ve used great white bennies a little bit but I’m not convinced its compatible with dwc as it seems to leave build up on bottom of pots. The plants seem to have overcome the slime if that’s what it was. I’m still not sure as the pic shows slightly off colour roots with mild looking slime building up above water line. But it’s all cleaned up now after 15ml of h202 water level increased and dropped chiller temp to 20 degrees.

Usually - in my limited experience - if you are seeing discoloration at or near the water line - especially, in your case where you have a lot of water movement/splashing, immediately above the water line - the discoloration is caused simply by stuff that floats/gathers in the surface film layer and collects on the roots. Usually not an issue in that case.

What kind of nutes are you using again?

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I’m using gh maxi series (dry nutirients)
and gh additives lineup as well. Seems to do the trick so far

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