Anyone running HID/LED? what’s with the pastel colours?

f-e said:

Still wanting more I think. How high have you been? The Mg looks to be your real issue and it's kind low in your 5:1.5 so you may have to take it up with some epson salts to stop the Ca competing.

Other clues are them chucking out roots to find food, and the low light level plants being happy. I'm actually vegging some great looking plants on 10w per foot of cob and wish they would slow down a bit as I'm not ready for them. That power level would be crazy under hids. It's hard to believe without seeing it. I could want for nothing more.


I have some 5:2.5 and I'm using 1.5ml per liter. Mid bloom I have been sticking 1.5g of epsom in each 10L of water, which is like another 1ml per liter of that 2.5 so I'm really stacking it in. It's Mg I struggle with which seems to be pushed out by the K and if I push up the Ca also it hinders the Mg. Most bottles are between 2:1 and 3:1 and yours is 4:1 and I'm playing around the 1.5:1 mark.

Many people will have a knee jerk reaction based on the published ratio's from long ago. We don't believe in that in the UK. Things just need enough. Whatever that is. LED's are not going to comply with the old ideas as it's not a heat based light. Straight away we add calmag to anything. That ratio stuff says the K must come up, but that's just defeating the object of the exercise. They need Mag. Then perhaps N and P but we need a look at them with the Mg first. All added up... you can see why many people increase base by 40% as a blanket treatment. Or you could lower the illumination. You have seen you can walk but not quite run yet


Just noticed that 1% N in your calmag. I have 3% in both mine. For about 7L in a bucket I'm using 50ml of my base containing 2% then 10ml of my calmag with it's 3% so that's 15% more N from the calmag and my N-acid is offering up 10% more (which helps carry some unknown hard tap) So I have a 25% N increase and I have on occasion added some urea when using my flower up to week 4. My food just worked with HID's but did show Mg if the salts were a bit high.

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GanjaMisfit said:

I had symptoms exactly like yours when I switched from hps to using led/cmh combo and it was temp/ humidity related. My room/leaf temperatures and humidity were too low. I got my VPD sorted out and my plants responded soon after. I didn't see where you stated your tent temperature and humidity but certainly can cause issues

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browntrout said:

19-23c 50-60% humidity

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browntrout said:

All interesting stuff, and that may well explain it. However after feeding calmag at full strength for water and feedings there really wasn’t a change, The same issues still maintained and perhaps worsened. I understand they might need more Mag. I stopped using the calmag in the last week, convinced the light strength or spectrum strength was causing the issue and the plants actually seemed to do better not using it.

I’m just having a hard time seeing how 300w of LED is creating an issue that 250-300ppm of cal/mag won’t even show an improvement. I think moving the lights up until I get proper growth surpassing the 20w growth and then coming back to the calmag might be ideal.

Likely a full strength dose of nutes could help.

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GanjaMisfit said:

Seems too cold to me. What's your leaf temperature? With led/cmh combo my leaf temperatures run 6 to 7 degrees under my room temp. When I ran straight hps my leaf temps were the same or higher than my room temps. I can run my room at much higher temperature now without issues associated with heat stress that hps would give at the same temperature. Anyways not saying thats your issue but it was for me and something to consider.

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f-e said:

Glad you came by. I thought we had that covered but should of gone back to the beginning. That's freezing even with a more suited 45-50% for them temps. 60% at 28c makes them grow. Under 25c you can root cuttings but as soon that they need to eat it's too cold for a rapid growth attempt.

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GanjaMisfit said:

When I see plants that look like the op pics especially in the winter I have to ask about temps. Those plants look cold to me. You need to have your basic environment under control before we can diagnosis nutritional deficiency. But I totally agree with you if the op gets his temps up with a calmag bump he will see a big improvement!

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Lapides said:

I've been growing under leds for a couple years now and I have seen A LOT of what you're seeing now. I am FINALLY getting beautiful plants after adding 1 gram of epsom salts per gallon of water to my watering routine.


I followed the suggestion at the bottom of this page - https://www.pacificlightconcepts.com/led-tips/

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f-e said:

iirc that's the kind of ppm I'm having to use, but with care to not push out the Mg with Ca or K which I couldn't do with your 4:1 ratio. I have tried. The Mg wants increasing in relation to the Ca, but at 4:1 the ratio science says you are pushing the Mg down in relation to the Ca. So you don't get anywhere.

Mg is very soluble. With excess salts the first signs I see of over feed are Mg deficiency.


Dimming the lights is a sure fix it seems. Then maybe start pushing them to see what shows first.



VPD isn't very intuitive. It's not like drying towels. Though I keep treating this topic that way. A decent healthy plants will open it's s-tomato's in a more humid environment, and drink more than in a dryer one if drier was so dry it was uncontrollably so.

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Lapides said:

I doubt you're getting accurate pfd readings from a light meter app.

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f-e said:

Interesting to hear someone using the same sort of epsom based Mg I speak of, but without the Ca. I will read the link shortly. I feel the 3:1 ratio is still too much Ca to let the Mg get a big enough share in the cec stakes. 1.5:1 isn't a bottle I found, it's progressive learning and I am actually looking at the idea it's too much Ca during stacking though alright at other times.

Many light meters and as such perhaps the apps won't measure the full spectrum. They will just pick a band of red or green and know the rest as it's presumably sunlight. Even the expensive quantum meters have correction values published for each model when using LED's. Though no specific LED's. So are essentially not that good either. The 4 fold difference may suggest the app is for sodium lamps and centered on the red/orange boarder where they perform so well and LED are not trying.

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f-e said:

That's an excellent question I can't answer as well as I would like. What I do know..

Nobody has ever knocked epsom as an Mg source due to problems
S is gaining attention as it influences flavour considerably.

Rightly or wrongly I have been trying to introduce it along with a Ca source because it has that S that calmag doesn't.

That link was a surprise. They believe LED just leads to heat and Mg needs. No talk of Ca which is what everyone else seems to be finding lacking. Then here I am looking at 1.5:1 thinking my Mg could go higher but looking to my peers to find I'm on shaky ground. Your plants (should I look again..) seem to also be asking for Mg mostly.

I must of looked at 8 different calmag supplements in my mate shop and non passed the 2.2:1 ratio which seems unrepresentative of an LED growers needs. However Ca is many peoples issue so just an Mg correction seems short sighted

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