Everything everywhere says 5.5-5.8 ph is ideal, is that incorrect

Hello, I have a calcium issue during my 6th week of flower on some blue dreams. This is only affecting 10% of the flowering crop. But it’s bad. I have added more calcium but I haven’t seen it halt. Recently I came across ILGM PH chart, it says that calcium uptakes starts at 6.0 PH. We currently use a ph controller at 5.7 ph. Which would limit the uptake since we don’t allow the water to get to 6.0.

Should I just run at 6.0? From the

chart it looks like every nutrient still is available at 6.0. I almost feel that running at 5.7 in veg then bumping to 6.0 in flower would keep this from happening. This happened on my last round and I misdiagnosed and changed too much for too long. It affected the harvest badly. I’m not overreacting this time but I’m worried as some of these girls have been building so nicely.

I want to fix ASAP but don’t want to cause another issue so late in flower.

My set up:
Tap water at 25ppm to start.
Emerald cal mag at 2ml per gal
We run flow tables with 16 plants each all in pots w clay pellets. We water every 45 min for 10 min. Ran from a 70 gal res. Feeding two tables each.
We also have a 26 bucket RDWC.
we use AN ph perfect three part base and the AN flower additives such as big Bud and candy. We also rotate b52 and voodoo.

Plants on both the tables and buckets are showing the signs.

My pic is not the best I’ll get better shortly.

We maintain flower ppms around 1000 and keep PH steady at 5.7. Water temp is 67-71. Air stones everywhere.

If the calicium uptake issue is corrected should I see rebounds of those plants for thier last few weeks of flower?

Thanks all🙏🏻

I can get some leaf pics after dark today.

@TDubWilly @Bogleg @WickedAle @Myfriendis410 are some very knowledgeable hydro guys. Welcome to the forum I’m sure help is on the way. Pics downloaded one at a time in regular light will help to diagnose your situation. Good luck :four_leaf_clover:


Welcome to the forum! Ph requirements and uptake between a hydro grow and a soil grow are going to be different.

Also, damaged leaves won’t correct themselves. So when you have an issue those leaves are pretty much shot, you’ll have to watch your newer growth to have indication of whether issue is better or not. One more thing, I’m not sure if you’re using ph adjusters with the ph perfect nutes? I’ve read several issues in doing that.


Won’t hurt anything.

My water has a tendency to slowly drop in pH anyways so I normally pH to 6.0 in the mornings and when I get home it’s 5.8ish.

pH to 6.0 but learn your chart and keep an eye out for deficiencies that are susceptible in that range.


I find the 5.5-6.5pH range to be acceptable and don’t fret over minor pH deviations from 5.8


I also like to be on the high end of the hydro PH scale or a hair above: I like 5.9 using GH Lucas formula.

Six weeks into flower I might reduce or even discontinue cal mag; deficiencies are normal at this point in the grow…


Turns out the issue I’m here! get a move on!! Only on my grape kush. They share res w blue dream which have zero signs of deficiency. Pics are of two plants. The leaf is from the second plant. Buds are growing and fattening up still.

We are allowing the ph to rise to 6.0 on the controllers.

What are yalls thoughts on the pics?

Thanks so much for your sharing, it’s much appreciated! :pray:t2::pray:t2::pray:t2::pray:t2:

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Forgot a pic. This is where the single leaf pic came from. These are my worst showers of the issues.

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What is your ppm? Did you add any nutrients that contained sugars or organics? What do the roots of each plant look like? Thinking microbe attack, I can’t tell from leaves. You would be abl,e,to see it on the roots and possibly the stem in the netcup.

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The roots are Snow White and perfect. These all share the same res. So microbs would be everywhere. These two are even the only ones within a 26 or 16 plant shared res.

However it’s happening on almost all the grapes, just more prevalent on the biggest plants. The smaller ones dont show it near as bad.

We did add AN candy which is a sugar I suppose… These are two of the largest plants. With the biggest colas. And they still are fattening.

We ran ppms at 1300 for two weeks at weeks 3-4. But now are dialed back to 800-850.

Roots looks so happy. Some are in a flow table exposed they look 100. And the buckets are perfect as well.

This happened on my last round w these grapes. So I wonder if the just eat crazy or I locked them out two weeks back and now they showing me what I did. Lol.


What does this mean? AN candy does contain sugar that is not compatible with DWC breeds bacterial blooms that depletes the O2 in the feed. Any slime on the walls of that reservoir?

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I have two strains. Blue Dream and Grape Kush. This issue is showing only on the grapes. The Blues show no signs of anything. But the blues flower longer, so they aren’t quite as developed and as far along into flower.

They share a res so I feel any root issue would be spread into both tables the single res feeds. Thus impacting the blue dreams. But, the blues are :100:
Idk, I don’t want to over think it but I need to get her what she needs so she (they) can finish as strong as possible.

It’s looks like a calcium issue to me the chart shows little to no feeding at 5.7. Which is where I have always tried to stay. The “sweet spot” 5.5-5.8 range wise. But now I’m wondering if this strain needs more calcium late in flower and my low ph at 5.7 isn’t allowing calcium feeding. I’m arriving at that conclusion based on the chart that shows no calcium feeding at 5.7.

I just hate seeing the girls struggle.

Yes I have some slime on the walls of the table res. The RDWC doesn’t seem to have any…yet.

Uploading: 07ECA745-BFF4-44FE-9573-C67BED1324C6.jpeg…


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Slime is an indication you have some anerobic bacterial growth. I’d check the roots for slime too. These bacteria are probably sucking down all of the O2 and is making the feed toxic. Maybe th blues are more hearty than the grapes to this root rot.


I have been using AN’s Piranha to avoid the slime in my hydro, high press aero and so far working great. I am almst 2 weeks into flower On my 1st hydro attempt. I keep my ph at about 5.7 but I DO let it climb to 6.2ish before I drop it back dwn to 5.7. I find it gives the plant to have more of a ph “range” so it get the nutes that need lower ph and then hits the nutes that require abit higher ph to absorb. I find 5.7-6.2 works good for me, I also use the same in my pro mix girls too.
My hydro is T99
Pro mix I have GSC, OGK and T99.
All almst 2 weeks into flwer and the only one showing cal mag issues is my T99 in pro mix. Just brought ph of T99 pro mix up to 6.1 run off today from 5.6 to see of it helps.
I would def bring ur ph up a point or 2 and see how thats goes.

Looks like it to me too, and i think it is, but it’s not always 100% obvious.

Possible leaf septoria, which I doubt, or even a fungus known as Rust.