# Making your own fruit fly media (problems with mold)



## staarbit (Aug 15, 2016)

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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## patm (Mar 21, 2004)

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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## Ed (Sep 19, 2004)

Cinnamon is probably being overrated in its effectiveness in the cultures. 

See http://www.dendroboard.com/forum/food-feeding/25730-fly-culture-media.html#post2122577 

some comments 

Ed


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## staarbit (Aug 15, 2016)

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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## patm (Mar 21, 2004)

staarbit said:


> 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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## Ed (Sep 19, 2004)

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. 


some comments 

Ed


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## serial hobbiest (Mar 5, 2017)

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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## Ed (Sep 19, 2004)

serial hobbiest said:


> 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. 

some comments 

Ed


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## serial hobbiest (Mar 5, 2017)

Ed said:


> 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.
> 
> some comments
> 
> 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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## Serafim (Mar 29, 2017)

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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## serial hobbiest (Mar 5, 2017)

Serafim said:


> 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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## Serafim (Mar 29, 2017)

how much are you putting in when you make a new culture?


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## serial hobbiest (Mar 5, 2017)

Serafim said:


> 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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## Serafim (Mar 29, 2017)

LOL I over did it a few times. I see recommendations of like 6-10 grains..


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## Ed (Sep 19, 2004)

Serafim said:


> 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. 

some comments 

Ed


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## MDfrog (Apr 2, 2012)

since I started using Josh's Frogs Methyl Paraben in my fly mix, i have yet to have any issues with mold.


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## serial hobbiest (Mar 5, 2017)

Ed said:


> 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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## Ed (Sep 19, 2004)

serial hobbiest said:


> 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.




serial hobbiest said:


> 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. 



serial hobbiest said:


> 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. 

some comments 

Ed


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## Pumilo (Sep 4, 2010)

If you want to see exploding flies, I think you need to spike your culture with flies *before* you put it in the microwave.


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## Mantid man (Feb 18, 2021)

staarbit said:


> 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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## Socratic Monologue (Apr 7, 2018)

Mantid man said:


> Dont use vingar !!! Vinegar is toxic to most bugs


It doesn't hurt FFs -- many media, homemade and commercial, use it. I use it, no problems.


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## Chris S (Apr 12, 2016)

Socratic Monologue said:


> It doesn't hurt FFs -- many media, homemade and commercial, use it. I use it, no problems.


I use white vinegar or apple cider vinegar in every single culture I make. No problems.


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## hypostatic (Apr 25, 2011)

Socratic Monologue said:


> It doesn't hurt FFs -- many media, homemade and commercial, use it. I use it, no problems.


drosophila are literally called vinegar flies. you can set traps to attract them with apple cider vinegar. i wouldn't sweat adding a splash of it to your media.


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## davecalk (Dec 17, 2008)

I have been using ⅛ cup water + ⅛ cup vinegar Total ¼ cup of moisture mixed into ⅛ cup of home made media since the 1980s with no issues or problems.

Vinegar is not toxic to flies.


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## kate_stpaul (May 28, 2021)

Ed said:


> 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.
> 
> Clash of kingdoms or why Drosophila larvae positively respond to fungal competitors - Frontiers in Zoology
> 
> ...


I'm resurrecting this convo, since it's closely related to the issue I'm having. Hopefully you can offer additional insight, @Ed. Or maybe @Socratic Monologue or @fishingguy12345? 

I have some white fuzzyish mold (with what looks like a greenish tinge? Hard to tell) in one fly culture, and I thought I might scrap the culture because the mold is still growing. However, lots of maggots have appeared over the last few days, which tells me the mold hasn't taken over and the flies are doing fine. I thought I read in another thread that it's ok to feed from the culture but not to make new cultures from it. So I don't plan to make more cultures from this one, but if it's safe to feed the flies to my frogs, is there any potential that they'll carry the mold into the viv -- and assuming I don't want this kind of mold in the viv? Or should I not feed from this culture at all? 

I haven't pinpointed the exact issue that caused the mold, but I'm new to culturing flies and definitely going through some rounds of trial and error. 🙂 I'm using NEHERP premixed media with vinegar and baker's yeast added as they recommend. But I'm sure I made some technique blunders somewhere on this culture and the previous one -- my first culture did great with no issues and produced quite prolifically. So 🤷‍♀️. I'm going to switch to Repashy Superfly and maybe tweak a few things in my process to see if I get better results. 

Tried to get a decent pic of the mold:


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## fishingguy12345 (Apr 7, 2019)

I'm no fruit fly culturing expert lol. 

I've never had an issue with mold in any of my cultures. 

I don't tend to like using "in the wild" but in the wild frogs would eat insects that have eaten all kinds of things including mold. I doubt it'll be harmful to your frogs .


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## Socratic Monologue (Apr 7, 2018)

If that species of mold is in your cxs, unless there's a biosecurity seal between it and your viv, that mold is in your viv too, but doesn't find the conditions in there favorable. 

I think feeding them but not seeding with them is a good way to proceed.


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