Fly Larvae in Fermenting Sub

PowerHobo

Chalcosoma
Should I be concerned, or will the sub likely be fine once it's done fermenting in 4-5 months and can be heat treated?

I'm currently working on my first batch of outdoor sub, and it's been going really well for a couple weeks (it's actually darkening up a lot quicker than my indoor batch did), but yesterday when I opened both containers to mix them, I found a couple dozen fly larvae on the surface of the sub, and probably another dozen stuck to the lids in the condensation. Didn't see any flies, so I'm not sure what kind they are. The might be pupae, but they're a little squishy for that, and I'm used to fly pupae being a reddish/brown color. These are about the size of long-grain rice, bright white (a couple are black, which I assume are dead), and none of them are moving at all.

 
Probably fungus gnats, yes the pupae are a reddish brown, and the reason they aren’t moving is likely because they’re mature and are getting ready to pupate

 
If the substrate is actively fermenting, they're most likely the early instar larvae of the Black soldier fly (Hermetia illucens).  They won't affect the quality of the final product.  In fact, they might even help speed up the fermentation process up by secreting digestive enzymes.  They can, however, become very numerous.  If they are soldier fly larvae, they'll soon get a LOT bigger than a grain of rice, and will have a somewhat armored appearance.  If they're appearing in your fermenting substrate, it might possibly mean that it's not getting quite hot enough (the larvae are killed by temperatures above around 113 F).  If you are only fermenting small batches, the temperature might not get above that, of course (although, below 113 F is possibly still adequate for the process).  If the substrate is turning from tan to brown, it's working.  Yes - outdoors in the summer is definitely the best way to go for fermenting substrate, as it's difficult to get a high enough temperature indoors to get it to work properly (and of course, there's the overwhelming, sour smell that occurs when the process really gets well underway).  I put my fermenting substrate right out in full sun for maximum heat - those thermophilic microbes get a real boost from it, and it helps speed things up.  The fermentation stage of the process can finish in as little as 4 weeks this way, but of course, you then need to let the material sit for at least 2 months (preferably 3 or more) afterward to fully "mature" and be ready to use.  The longer it's allowed to sit, the darker it will get.

 
I've actually been noticing that that this batch has already stopped smelling like sour wine and already has a bit of soil smell to it. It definitely still needs to darken up, though. The daytime temp hasn't been below 98f for quite a while, and we're looking like an average of 108f over the next week. I just started my first batch in a 2-chamber tumbler last night, so we'll see how that goes (if all the sub doesn't leak out of the air vents, that is).

 
Just cover the air vents with weed cloth. I use hot glue and it seems to work fine. None of the substrate will go through the weed cloth but it will still let the air through.

 
Are you supposed to cover the fermenting container with a lid?

Here's mine and I used Oak Pellets, Great Value Unbleached All-Purpose flour, and active dry yeast. 

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Are you supposed to cover the fermenting container with a lid? Here's mine and I used Oak Pellets, Great Value Unbleached All-Purpose flour, and active dry yeast. 
Actually, it's better to let it breathe, but where I am (and probably where you are; Tucson is dry and hot), I have to put a lid on it, or it dries out way too much in just a day's time. If you're mixing every day, you should get plenty of air exchange in the process of turning it.

If you haven't tried it before, you should give wheat bran a try as a replacement for the flour. The general consensus here seems to be that the bran yields better/more thorough fermentation, and that appears to be true in my (admittedly limited) experience.

Just cover the air vents with weed cloth. I use hot glue and it seems to work fine. None of the substrate will go through the weed cloth but it will still let the air through.
I completely forgot that you had previously advised me on this in DMs. I definitely need to get on this. The actual vents in this thing have rotating doors and aren't so bad, but every hand-hold (and there are a lot) has 2 sizable holes, and that's where most of my leakage is occurring.

 
Do you keep it moist at all times? 

Also sorry for hijacking your thread. I barely started yesterday. 
No worries! Everyone starts somewhere; I'm barely into this hobby myself, and it's only through the help of the people on this forum that I've been able to successfully ferment substrate.

From what I understand the bacteria that cause fermentation thrive in warm, moist environments. Decomposition creates moisture as it progresses, so it doesn't need to be too wet to start with if you're using a lid like I am. I start my mixture just barely moist enough to be compactable, and it ends up pretty moist by the time it's most of the way there.

 
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