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Hey, guys! I recently attempted for the first time to mix my own fruit fly media in order to try and cut back on costs, especially for future purposes because I do plan on getting more frogs eventually. The media I normally use, however, has a mold inhibitor while the media I made myself does not. I didn't think it would be a huge deal but I made my first culture with my personal media just to test out the recipe and see if it worked for the flies and it only took 3 days for it to be completely and utterly overgrown with mold. I even sprinkled some cinnamon on top as the recipe for the media suggested in order to cut back on mold growth but that did not work at all. Is there any way to fix the mold problem?
 

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You could add a commercially available mold inhibitor, like methyl paraben. You could also try using a sprinkle of bakers yeast in new cultures. Last, try using vinegar when mixing up your media.

Personally, I always nuke a newly mixed culture in the microwave for 30 seconds to sterilize it the best I can (obviously before adding flies). I also make sure I use boiling water to mix the dry ingredients. However, if you're adding mold by introducing flies from an infected culture, these precautions may not work. You may have to order some new, clean cultures to start over.

Pat
 

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Discussion Starter · #4 ·
Thank you both for the replies! I think I'll give the vinegar a shot first just because I don't want to have to buy the mold inhibitor and I actually have vinegar on hand. Does it matter what kind of vinegar? Does it have to be just standard vinegar or would apple cider vinegar be okay?
 

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Thank you both for the replies! I think I'll give the vinegar a shot first just because I don't want to have to buy the mold inhibitor and I actually have vinegar on hand. Does it matter what kind of vinegar? Does it have to be just standard vinegar or would apple cider vinegar be okay?
I believe apple cider vinegar is often the preferred go to.

Pat
 

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I greatly suspect that the vinegar addition is nothing more than feel good tactics as many of the molds that can get into the cultures does just fine at those pH's and some can even reduce the pH even further (Aspirgillus niger takes it down to a pH of 2) as a method to deal with competing microbes.


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Ed
 
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Just thought I'd chime in here with my fly culture mold experience. I've been culturing flies now for a couple months in practice before acquiring my first frogs. Until a week ago, I've been using a mix of just instant potato, nutritional yeast, spirulina, cinnamon, & vinegar (& water obviously) with no mold problems whatsoever. I've had consistency with production issues with the mix, however, and it was pointed out to me that I should be using sugar. It was also pointed out that my mix may be deficient in a few carotenoids for the frogs' benefit. It was around here when I ordered some Repashy Superfly to try out, but in the meantime, I need to keep the cultures cycling. So to my original recipe I added sugar, paprika, beet root powder, and after mixing it up in the jar, I finished it off with a sprinkle of active bakers yeast.

To this culture, I added young flies (not first emergers, but after culling the first emergers... I used flies that emerged maybe 5 days or so later). Anyhow, I was watching this one carefully, and the media looked as stable as any for a whole week while the flies matured. At five days old, there were no eggs yet. At a week old (yesterday), there was a nice layer of eggs across the surface of the media. This morning I have some white mold growth in there. I'm not too happy about that, because this culture was intended for feeding of actual frogs I'm getting at the end of the month.

I wish I could say definitely what the cause of the mold was. I suspect all the extra nutrients in beet root powder might be the root of the problem(<---- HA! Get it?!), or maybe I just used too much.
 

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I have some white mold growth in there. I'm not too happy about that, because this culture was
Is it white and fluffy or white and slimy? You can probably still use it to feed out. Normally there is contamination on the tools you use to make the cultures or structures like excelsior or coffee filters.

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Is it white and fluffy or white and slimy? You can probably still use it to feed out. Normally there is contamination on the tools you use to make the cultures or structures like excelsior or coffee filters.

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Ed
It's a tad fuzzy looking, and really thin. Doesn't seem too aggressive. I'll also mention at this point, the sprinkle of bakers yeast I added to the top of the media didn't stand a chance vs. all those flies in there. I wasn't sure what to expect exactly, but it certainly did not get a chance to spread across the surface as I figured it might.

On an unrelated note, have you ever seen a fly explode? I'm sitting here looking at this culture, and I've got this one fly roaming around in there as red & bloated as a completely engorged mosquito. Like an obese wiener dog, its little legs can barely touch the ground, and it drags its belly when it walks.
Can fermentation happen in the gut of the fly? Maybe it's having trouble farting, and will eventually pop from CO2 build-up. Poor little guy :(
Or maybe it just really likes beets? I don't see any other red-bellied flies in there, let alone any oinkers like that one. What do you make of that?
 

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sounds like too much bakers yeast mine did that when i used too much. I have since stopped adding it to new cultures and rely on the flies from older cultures to transfer yeast
 

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sounds like too much bakers yeast mine did that when i used too much. I have since stopped adding it to new cultures and rely on the flies from older cultures to transfer yeast
Yeah, I was wondering if that's what it was. I suppose it could be yeast, but it looks too white... unless that's because it's so thin. Or maybe it's a wild yeast? I know Brettanomyces is white... The culture doesn't smell of mold either- still nice & fresh smelling actually.
 

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how much are you putting in when you make a new culture?
It was just a pinch scattered over the surface, as if I was salting my dinner plate. I also hit it with a shot of mist to get it started, but as I mentioned it had disappeared in a day or so. Obviously the flies wouldn't have gobbled up every last cell though.
 

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sounds like too much bakers yeast mine did that when i used too much. I have since stopped adding it to new cultures and rely on the flies from older cultures to transfer yeast
Its pretty hard to add too much baker's yeast. I ran some anecdotal tests and even a tablespoon on the surface didn't change how the culture ran over time.

If the mold is staying pretty small, the maggots will churn it under fairly quickly. They actually have behavioral responses to help control molds on their foods. See for example Rohlfs, Marko. "Clash of kingdoms or why Drosophila larvae positively respond to fungal competitors." Frontiers in zoology 2.1 (2005): 2.

https://frontiersinzoology.biomedcentral.com/articles/10.1186/1742-9994-2-2

https://www.researchgate.net/profil..._resources/links/0912f5131c904afbf2000000.pdf

Rohlfs, Marko, Björn Obmann, and Ralf Petersen. "Competition with filamentous fungi and its implication for a gregarious lifestyle in insects living on ephemeral resources." Ecological Entomology 30.5 (2005): 556-563.

Keep in mind that adding the yeast speeds up egg deposition as this is an oviposition cue for the adults.

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Its pretty hard to add too much baker's yeast. I ran some anecdotal tests and even a tablespoon on the surface didn't change how the culture ran over time.
At this point, my money is on baker's yeast, not mold. It has formed little ball shaped colonies just like it does in a petri dish of agar wort. I find it a little strange how it all seemed to disappear at first only to return with a vengeance after 6 days, though. I'm skeptical that having all this thriving baker's yeast in there is beneficial in terms of growing nutritious flies. Wouldn't its constant replenishment be diluting the more nutritious nutritional yeast in there? Does it stand to reason that the final emergence of flies might be a little deficient considering the nutritional yeast can't replenish itself? Perhaps the culture will produce longer, but who cares if the flies are bad feeders? Could this be why there is no active yeast in Repashy Superfly (with warm water mixing instructions, ofc)?

If the mold is staying pretty small, the maggots will churn it under fairly quickly. They actually have behavioral responses to help control molds on their foods.
Well that's interesting, and good to know.
So, you've never seen a fly explode, eh?
 

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that having all this thriving baker's yeast in there is beneficial in terms of growing nutritious flies. Wouldn't its constant replenishment be diluting the more nutritious nutritional yeast in there?
Not really... the nutritional yeast is another strain of Saccharomyces cerevisiae... and the addition of the nutritional yeast is to get the flies over the initial hump by supplying an adequate protein source until the other strains (carried by the flies) get going. There are going to be changes to the strain of Saccharomyces cerevisiae in the media as the flies are going to bring variations that are more adapted to the culture conditions in your cups which is probably going to outcompete the strain of baker's yeast added to induce faster egg laying and reduce unwanted microbial colonizers.

Stamps, Judy A., et al. "Drosophila regulate yeast density and increase yeast community similarity in a natural substrate." PLoS One 7.7 (2012): e42238.


Does it stand to reason that the final emergence of flies might be a little deficient considering the nutritional yeast can't replenish itself? Perhaps the culture will produce longer, but who cares if the flies are bad feeders? Could this be why there is no active yeast in Repashy Superfly (with warm water mixing instructions, ofc)?
Even if you purchased Carolina Bio Supply company, there isn't any active yeast in it... keep in mind as you noted all of the medias that require the addition of hot water or microwaving the culture makes adding live yeast at that time moot.

The flies adapt to changing conditions by reducing body size in response to decreasing nutrients and water but keep in mind that that larvae are also digesting the dead flies, pupal shells and even wood products through the excretion of enzymes. Now it is possible that these are deficient in certain nutrients but if you have cultures that produce multiple generations you can select which cultures to use for your frogs.

Well that's interesting, and good to know.
So, you've never seen a fly explode, eh?
I've never seen one explode but I'm pretty sure that there is a mutation that results in a swollen/bloated body.

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Ed
 

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If you want to see exploding flies, I think you need to spike your culture with flies before you put it in the microwave. :eek:
 
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Thank you both for the replies! I think I'll give the vinegar a shot first just because I don't want to have to buy the mold inhibitor and I actually have vinegar on hand. Does it matter what kind of vinegar? Does it have to be just standard vinegar or would apple cider vinegar be okay?
Dont use vingar !!! Vinegar is toxic to most bugs
 
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