Chlorine for sterilising nutrient solutions, Coco DTW

VictorFlorez

VictorFlorez

Member
So I’ve tried using H2O2, 50% strength solution, at a concentration of up to 0.2mL per L, which has not been effective in getting rid of white mold growing on the Coco. Surprisingly, grape seed extract has proven very effective at removing visible mold.

Although GSE has worked for visible mold growing on the top of the medium, as it does for trays of wheatgrass, I don’t have confidence in it’s overall efficacy and using it long term, and there is still a fair bit of biofilm in the runoff.

I am looking at trying calcium hypochlorite next, I do not want to use bleach, and the only bleach available always has sodium hydroxide added anyway… The only products I can access are commercial “pool shock” products, so far they have all proven to be quite vague about what exactly is in there.

As far as I can tell, there is one granulated chlorine product which seems superior to the others, in that it doesn’t have multiple additives. Aside from 70% calcium hypochlorite, it contains “isocyanurates” , and I was told these are not suitable for plants. Is this product suitable? The link I will share doesn’t mention the isocyanurates, but if you read the label on the back it mentions it.https://www.bunnings.com.au/hy-clor-2kg-super-shock-granular-chlorine_p3093676

TLDR: The pool shock I am looking to buy is vague about what the ingredients are, but mention ~70% calcium hypochlorite including “isocyanurates”. Is this still ok to use? The guy at the hydro shop said chlorine with isocyanurate in it is not ok to use, but I hate going there because I’ve been given bogus advice before and always take what they say with a grain of salt.

Thank you!
 
VictorFlorez

VictorFlorez

Member
MickFoster said:
Is the alleged white mold causing problems with your plant?
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I believe so. Although not dramatic, there’s some minor leaf curling/twisting on two plants, and yellow spots appearing on some lower leaves. There’s a large amount of biofilm and slime in the runoff, also a smell of mold.
 
VictorFlorez

VictorFlorez

Member
I’m wondering if this Pool shock product, “70% calcium hypochlorite, with cyanuric acid as a stabiliser” is safe for the plants. Any idea?
 
rkymtnman

rkymtnman

Well-Known Member
VictorFlorez said:
Perfect. I’m trying to figure that out right now based on what your using, but I’d be keen to hear what he reckons.
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i think these calcuations are based off 62 or 64% hypochlorite but it's 0.10 grams per 10 gallons is 1ppm chlorine. up to 5ppm is safe for plants and humans
 
VictorFlorez

VictorFlorez

Member
rkymtnman said:
i think these calcuations are based off 62 or 64% hypochlorite but it's 0.10 grams per 10 gallons is 1ppm chlorine. up to 5ppm is safe for plants and humans
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Thank you @rkymtnman , I’ll make it a sticky note. My math isn’t great, but from what I understand, 64% at 0.1g per 10 gallons = 1ppm, that should mean bk’s exact same ratio with 70% hypochlorite will still be within the safe 5ppm-max range.

Will be trying it out in a little while when the R/O unit finally fills the res. I’ll sit down with a calculator and get the exact numbers soon, but roughly for now: For 16L, dissolving 0.35g cal-hypo in 100mL water, and using 10mL of that dilution per 16L for around ~0.035g/16L. 9mL at first if I want to be super careful. Should be no worries. Much appreciated everyone, thank you all.
 
bk78

bk78

Well-Known Member
VictorFlorez said:
Thank you @rkymtnman , I’ll make it a sticky note. My math isn’t great, but from what I understand, 64% at 0.1g per 10 gallons = 1ppm, that should mean bk’s exact same ratio with 70% hypochlorite will still be within the safe 5ppm-max range.

Will be trying it out in a little while when the R/O unit finally fills the res. I’ll sit down with a calculator and get the exact numbers soon, but roughly for now: For 16L, dissolving 0.35g cal-hypo in 100mL water, and using 10mL of that dilution per 16L for around ~0.035g/16L. 9mL at first if I want to be super careful. Should be no worries. Much appreciated everyone, thank you all.
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I’ve upped it as much as .30g and haven’t noticed any difference at all. When I open my reservoir lid it smells like I’m at a pool
 
VictorFlorez

VictorFlorez

Member
PJ Diaz said:
Why not use a bacterial based fungicide, such as Southern Ag Garden Friendly Fungicide? Are you sure it's mold?
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I mean, I’m fairly sure it’s mold of some kind. It’s white and fuzzy, it smells like mold, it’s growing all over the top of the coco and spreading throughout, I let the top dry out occasionally to try and keep it away, but I can see it around the bottom of the drain holes where roots are starting to poke out, and fungus gnats have begun showing up.


I like the idea of beneficial microbes. That southern Ag product is unavailable here. I was using Great White mycorrhizae from the start, rolling root balls in it at transfer, top dressing with it, and putting some in the feed every two weeks or so. The res would get slimy, and the air stone ended up looking like it had boogers coming out of it, but it smelled fine. I would only keep a nutrient solution in it for a max of 3 days too, before making a fresh batch.

This white mold started growing pretty aggressively on the jiffy pellets I germinated in, and eventually spread to the coco. I didn’t think it was anything to be concerned about at first, as the plants seemed ok, and thought it was a normal part of using the bennies.

…But eventually the smell changed, becoming noticeably moldy and unpleasant, leaves started developing yellow spots. It took over and I noticed that the mold is highly hydrophobic, almost waterproof. Water would bounce right off it. Also, the runoff was getting super funky and loaded with slime.

So I made the decision to try hitting them with H2O2 as per some advice from another RIU member, which worked at first. The mold vanished after 3-4 applications of nutrient water with added H2O2. I started adding it to every watering. Things went alright for a couple of weeks, and just when I thought I could stop adding H2O2 and begin using the bennies again, mold started growing back with a vengeance. This time with a stronger smell, and more leaf issues + runoff funk that clogs up the tubing I use to suck up the runoff. Upping the dose of peroxide didn’t help.

So while I love the idea of natural, organic, using beneficial bacteria, etc… Indoors, I have had nothing but problems trying to do it that way so far. I actually looked for something like southern AG a couple weeks ago, and couldn’t find anything similar here available commercially. I still do most things as organic and natural as possible, and I might have given Southern At a go before going down the chlorine road, but at this point I just want to start running a sterile system and be done with all these issues. Maybe I’ll have better luck next time.
 
VictorFlorez

VictorFlorez

Member
bk78 said:
I’ve upped it as much as .30g and haven’t noticed any difference at all. When I open my reservoir lid it smells like I’m at a pool
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Aw, I just added the chlorine to my res and ngl am a little bit disappointed it isn’t enough to get that pool smell. Let’s see how this goes!
 
7CardBud

7CardBud

Well-Known Member
I fish tank style UVA sterilizer should work well in a rez.......not sure about controlling molds on the media surface though.
 
PJ Diaz

PJ Diaz

Well-Known Member
VictorFlorez said:
I mean, I’m fairly sure it’s mold of some kind. It’s white and fuzzy, it smells like mold, it’s growing all over the top of the coco and spreading throughout, I let the top dry out occasionally to try and keep it away, but I can see it around the bottom of the drain holes where roots are starting to poke out, and fungus gnats have begun showing up.


I like the idea of beneficial microbes. That southern Ag product is unavailable here. I was using Great White mycorrhizae from the start, rolling root balls in it at transfer, top dressing with it, and putting some in the feed every two weeks or so. The res would get slimy, and the air stone ended up looking like it had boogers coming out of it, but it smelled fine. I would only keep a nutrient solution in it for a max of 3 days too, before making a fresh batch.

This white mold started growing pretty aggressively on the jiffy pellets I germinated in, and eventually spread to the coco. I didn’t think it was anything to be concerned about at first, as the plants seemed ok, and thought it was a normal part of using the bennies.

…But eventually the smell changed, becoming noticeably moldy and unpleasant, leaves started developing yellow spots. It took over and I noticed that the mold is highly hydrophobic, almost waterproof. Water would bounce right off it. Also, the runoff was getting super funky and loaded with slime.

So I made the decision to try hitting them with H2O2 as per some advice from another RIU member, which worked at first. The mold vanished after 3-4 applications of nutrient water with added H2O2. I started adding it to every watering. Things went alright for a couple of weeks, and just when I thought I could stop adding H2O2 and begin using the bennies again, mold started growing back with a vengeance. This time with a stronger smell, and more leaf issues + runoff funk that clogs up the tubing I use to suck up the runoff. Upping the dose of peroxide didn’t help.

So while I love the idea of natural, organic, using beneficial bacteria, etc… Indoors, I have had nothing but problems trying to do it that way so far. I actually looked for something like southern AG a couple weeks ago, and couldn’t find anything similar here available commercially. I still do most things as organic and natural as possible, and I might have given Southern At a go before going down the chlorine road, but at this point I just want to start running a sterile system and be done with all these issues. Maybe I’ll have better luck next time.
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If mold is coming back, that means that it's all over your environment. You might consider doing a sulfur burn to kill the spores in all the nooks and crannies. Are your pots getting proper drainage?
 
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