? Mold ? growing on tops of rockwool cubes

[Maculele]

I noticed some white powdery/globular substance on my clone plugs soon after I transferred them into rockwool upon going into my 2'x2' tray. Wasn't going to worry about it... Today I was moving some plants around to get optimal light distribution and I noticed a strip of similar looking stuff on the side of one of my rockwool cubes. I'm wondering what the stuff is and if it's a problem. It seems to wipe away (from the plugs and the rockwool) when I rub my finger on it, but nothing seems to come off onto my finger. It might be rubbing into the substrate, so I stopped doing that... Here's the standard infirmary questionnaire...

How long has this problem been going on?
Since placement into the flowering environment, the problem seems to be only evident on parts of the substrate that receive direct light.

What STRAIN are you growing? Pot of Gold

What was the establishing technique? (seed or clone?) Clone

What is the age of your plants?
Since cloning, 6-8 wks. Since placement into a growing environment, 1+ week

How Tall are the plants? 6-8"

What PHASE (seedling, vegetative or flower) are the plants in? Flower

What Technique are you using? SOG (no veg time except the stagnant time when the clones had nowhere to go, which was probably 5 weeks under low fluoro lighting and no nutes, just water

Growing system? Flood and drain in a 2' x 2' table

What substrate/medium are you using? Rockwool

What Nutrient's are you using?How much of each with how much water?
PBP Grow 6 mL/ gal
PBP Bloom 6 mL/ gal
Liquid Karma 5 mL/ gal
Cal Mag 5 mL/gal
BioBizz Root Juice 5 mL/ gal

How Often? Was 3 x 15 min floods a day, but I brought it down to 1 x 15 min flood per day. The rockwool seemed plenty moist.

What is the TDS/EC/PPM of your nutrients used? Don't know

What is the pH of the "RUN-OFF"? Perfect, 5.5-6.2 ish

What method of pH test was administered? Liquid drops in vial

What size bulb are you using? 600w HPS

What is the distance to the canopy? 2 ft.

What is your RH Factor? (Relative Humidity) ~50%

What is the canopy temperature? 93 F

What is the Day/Night Temp? (Include fluctuation range) 93 F day and 74 F night... big swing in temps right now. I'm correcting it for now by raising AC temps during the girls night cycle and running it hard during their day. Just started that

What is the current Air Flow? 4" 147 cfm can fan pulling thru a can filter located in the tent. Blows thru 8 ft. of 4" ducting. There's also a 12" fan blowing around the tent

Is the fan blowing directly at plants? Just above the canopy, they wiggle, but don't have leaves turned up or anything from massive airflow. The fan was added yesterday, which was approx. day 8 flowering.

Is the grow substrate constantly wet or moist? Constantly between wet/moist

Is your water HARD or SOFT? Neither

What water are you using? I'm using distilled bottled water. Buy it by the gal. at a local big box store

Has plant been recently pruned, cloned or pinched? They got a slight trim of yellowed leaves 3-4 days ago

Have any pest chemicals been used? If so what and when? NO

Are plant's infected with pest's? NO

OK so there it is... That's what's going on... Let me know what you think.
Also, the new growth on some of the plants in drooping/curling. You can see it in the pics. Check it out

Here are the pictures








Thanks for looking and for your input!

 

[Pseudo]

i would say it is a problem, other than switching to hydroton and lowering your temps 10 degrees, you might need to get some type of fungicide or h2o2 treatment, im sure somebody more knowledgeable will chime in

 

[Maculele]

Make that 85 F as the top daytime temp... Got that worked out.

Eh, I don't really think it'll be a big deal. The one plant is the only one that has any real quantity of it. I planned on using some H2O2 but was looking up how that should be done in rockwool. Anyone lookin', please let me know.

Also, the stuff on the tops of the plugs look different from what is on the rockwool. I'll keep checkin on them and keep ya up to speed

 

[Whatever]

Make that 85 F as the top daytime temp... Got that worked out.

Eh, I don't really think it'll be a big deal.

It's not a big deal IMO. The only hydro I ran for a little over 2 years was rockwool. There was some algae and all kinds of stuff growing on the tops of the cubes that were on top of the slabs. I started covering the cube tops with tinfoil and the algae went away, not much to begin with really and once the canopy filled in it pretty much went away anyway. The stuff that was growing on top of the cubes went away also. I didn't notice any difference in plant health/growth/yield or res ph and when I would cut the slabs up after I was done never noticed any difference in the root structure/health. Basically I think what I saw on the tops of the cubes was only a surface issue.

Thing for me was I was running feed lines directly into the slabs and the cubes basically dried out and all root activity was driven down below.

Not up on H2O2 concentrations for sprays but you can probably go really strong if just spraying the medium surface but I wouldn't bother.

As for the temps...in addition to air temps I would check slab temps with a decent probe type thermometer like you can get at a decent grocery or hardware store.

 

[Maculele]

Word. Thanks for the backup, Whatev...
I'm leaving them alone except for the neem addition I did yesterday. Since that stuff dies in suspension in water in as little as 24 hours, I'll do another run of it in about a week to try and knock out the rest of any mold or anything that's there. It can't hurt my girls, and I'd like to NOT have any funky shit growing in there if possible. I just realized I might be having smell issues here soon, so bigger problems are arising, it seems. I guess my carbon needs replacement... Strange, though, the filter should still be good.
They are looking OK right now. Still some yellowing, which I'm not happy about. I've hit them with some N lately, so that shouldn't be an issue, but I'll give them another dose tomorrow. I think I'll be changing out the res entirely tom, as well, so it'll be a good time to start them anew with nutes. I'll give them a healthy dose of grow but primarily bloom and the additives I spoke of before. It should help, I'd say...
Good luck, folks

 

[toodles]

A 147ft3/minute blower pulling thru a carbon can filter? 600Watts? Do you have a heat absorbing glass on the light?

No wonder it's hot in there. **IMO** you are woefully under ventilated. Maybe the A/C will bring temps down enough...However, I bet you'll still have an odor problem.

Toodles

 

[spiral]

It could be salt build up, seems the rooms a little warm and this could cause evaporation. The white stuff is the salt build up. I had the same thing once and tried everything to get rid of it, upon asking my hydro guy this is what he said. The water evaporates and leaves the residues behind. So I wiped my finger across the top of the cube and tasted it salty as hell. YUK.

 

[Maculele]

Yea, there's heat absorbing glass on my light hood. I wish I was aircooling, but since it's more efficient to pull through as opposed to push thru a carbon filter, I have it set up differently. I'm thinking about changing this up though, so that the heat will be pulled right out of the room.
I wouldn't call this woefully underventilated, though, because I had a room with more cubic footage years ago with the same exact equipment, no heat problems, plants were VERY happy. The heat was just due to no aircooling, having lights on in the hottest part of the day, and not running the AC effectively. Those things are handled now, and my lights on temps are around 86-88 at the highest now, and dropping with dropping outside temps. Between 86 in the ON time and 74 in the off time, I have a reasonable temperature range/swing.
I know it's not salts, its not a mineral looking build up, its fluffy and mold-looking. I wouldn't touch my finger to my mouth after I touched that stuff. If it's salt, and I'm wrong, not much problem there, I'll be flushing my tray tonight when I change the res out.
My concern right now is that some plants are growing faster than others, lots of moving around to do once lights go back on.

 

[Maculele]

No more mold growth... Neem application in the nute mix probably helped do the trick, but I'm not going to worry about it anymore. Growth seems solid, and I'll keep my eyes on the cubes to make sure
Somehow I got a ridiculously low pH tonight when I changed out the res, after having gotten perfect numbers until now with no modification. The only thing I did differently was use that Mr. Clean filtration system, which might be the culprit. I have no pH up, though, so they'll have to do with the small feeding of this unbalanced water until I can get some Lime and get things straight tomorrow.
Another case of, I bet they'll be OK, it's a damn weed after all. That's something I'm always impressed by, resilience of this plant.
Good luck to you all

 

[ItsGrowTime]

The hotter the room, the more humidity the room air holds. Your temperature is your biggest problem. A dehumidifier would do wonders for your room.

 

[Whatever]

Are you running a closed system?

 

[Maculele]

No sirree... It's passive intake, 147 cfm exhaust. Pulls thru a carbon filter that's in the room and blows out into another room. AC in the room that feeds the grow "tent" with air.

 

[Whatever]

Then a dehumidifier won't do shit. It does seem like your fan is undersized. A larger fan especially with a passive intake and especially if your passive intake is undersized will help both heat and humidity...and think your plants will be happier in general.

 

[Maculele]

I appreciate your continued input, whatev.
You think that a 147 cfm fan in a 30 cu. ft. volume tent is too little? After all, that clears the room about 5 times/ min. I ran the same fan, in a less efficient setup (blowing through the fan instead of pulling thru it) and yielded well with some excellent chron.
Still, I am using the same light, and in a volume that's smaller, I expect the temps to be higher, so I see your point in that way.
My humidity is at about 55%, should we consider that to be high?
I think that's probably good, and as the seasons change, the humidity will get lower as flowering goes on. That's something that I think is going to my advantage.
They're looking good, the only issue that I see right now is that the plants are not entirely equal in size. Most of them are about the same with 6 or so that are blowing up, mostly in height.
The mold (or whatever) is not really an issue anymore, as far as I can tell. Nothing has come back since I rubbed a neem solution on the top of the affected cube and added a small dilution of neem into the res.
The plants are lookin pretty good

 

[Maculele]

Also, even if the grow area isn't closed, a dehumi would help. If I put in in the air source room, the air coming into the grow area will have that much less humidity and logically the grow area will benefit.

 

[Whatever]

Also, even if the grow area isn't closed, a dehumi would help. If I put in in the air source room, the air coming into the grow area will have that much less humidity and logically the grow area will benefit.

The more air you have flowing through a space the less effective a dehumidifier is...how ever that works in your situation but the larger the dehumidifier the more effective it is in any situation...but still trying to remove moisture from flowing air is not advised...better air flow and/or heat reduction, will be more effective at lowering humidity in an open system.

Is that 55% lights on or off?

You think that a 147 cfm fan in a 30 cu. ft. volume tent is too little? After all, that clears the room about 5 times/ min. I ran the same fan, in a less efficient setup (blowing through the fan instead of pulling thru it) and yielded well with some excellent chron.

You have a fan rated at 147cfm but is it really performing at that capacity? There's lots of factors that affect flow...like running through a scrubber for starters. Doesn't seem like your fan/intake/scrubber/duct routing is up to snuff, for whatever reason, if you have a 'calculated' air exchange 5 times a minute yet your canopy temp is 93F...but read later it's now like 85F. I mean you shouldn't be over 80F and that's only air temp and not bud temps and there is a difference.

Did I read correctly in that you have a hood with glass yet not flowing air through it? That'll kill your bulbs for starters. Air cool the hood and both temps and humidity should drop. If you air cool the hood pick up some double foil covered mini bubble wrap insulating stuff from the hardware store and use 2 layers to insulate the hood...lots of radiant heat given off.

What type of 4" fan flows 147 cfm?

 

[Maculele]

Right, not as effective as possible, but a dehumi in this situation will work. I've done it with an acceptable degree of effectiveness. I don't think I'll be using one unless my humidity goes way up. The AC does what I currently consider to be enough of a job of removing moisture. Dammit, more stuff to buy later. It never ends, does it?

The glass on these light hoods still does a lot to absorb the heat generated by the bulbs even if no aircooling, so it's best to run with the glass. I can't imagine this decreasing the life of my bulb by very much, but maybe that is the case.

My intention is to begin aircooling next time lights are on, but it will decrease the efficiency of my fan because now I'll have to blow thru the carbon filter. No worries on that, I guess, I would assume the heat loss benefits will counter the slightly lessened air flow. I wish I had a flow meter to run some tests.

Good idea on the reflectix, I'll think about giving that a shot for sure. That's the kind of nitpicky stuff that'll get you thru the summertime.
I'm also thinking about rebuilding the tent setup. It's not quite pro enough, and I'm going to need to increase the internal volume soon anyway to add some soil girls.

And it's the 142 cfm 4" canfan. I stated that in the beginning. I keep quoting the cfm rating slightly off, tho. My bad

 

[DIGITALHIPPY]

LOL!!! thats not mold. thats chemical ferts collecting ontop.
ive had it before, grab a bucket of water (plain RO/distilled is best), or ph'd tap, and just pour it ontop fo the cubes. im assuming your running NFT drip with RW cubes-on-slabs.

 

[Weedman Herb]

Yeah ... salt build up ... that got covered on page 1 ...

 

[Hammerhead]

Where's the fresh air or co2?