# Fungus gnats in grow tank



## flyingSquirrel (Aug 22, 2011)

I have fungus gnats or something similar in a plant grow tank. I think they came in with a plant I had ordered.

They aren't too bad (yet). I just see one or two every few days.

I put multiple yellow sticky traps all over inside the tank, but I've only caught one gnat, and the other gnats I've seen just hang around elsewhere in the tank.

Does anyone know if there is some kind of stronger scent or something I can put on or near the sticky traps to draw the gnats to them?

I also looked at chemicals, nematodes, etc, but none of them sounded like a good idea (at this time, but maybe as a last resort)

Thanks for any help


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## nyskiffie (Mar 6, 2016)

No other animals in the tank? Can you do a CO2 bomb?


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## kimcmich (Jan 17, 2016)

Greetings,

Fungus gnats are ubiquitous and largely harmless. Even if you were to eliminate them now, you could easily end up with them again the next time you acquire plants or anything else packed with moist substrate.

I've never had a fungus gnat epidemic (others can speak to that possibility) - their numbers seem to be a persistent low-level in whatever size enclosures I have. So a first option would be to do nothing.

Pinguicula sp (butterworts) are carnivorous plants that work like natural (and very effective) fly paper. Fungus gnats come with the territory of growing carnivorous plants in their preferred moist media and butterworts are a great gnat eater.


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## nyskiffie (Mar 6, 2016)

What is the best method for growing butterworts (or other carnivorous plants) in a vivarium? I have some sundews I would be fairly interested in adding to my new viv but I heard they need practically soaking substrate which is not what I will be supplying in my viv. Should I plant one in a sealed pot in the background and keep it filled? Or will the mist be enough to keep it hydrated?


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## kimcmich (Jan 17, 2016)

Greetings,

A shallow dish set into the substrate or a closed-bottom container mounted on the background would probably be enough to give them the soggy conditions they prefer (assuming they get enough misting or you top them off every few weeks with water).
Most carnivorous plants want the brightest light you can give them - sundews and butterworts often grow in full sun conditions.


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## flyingSquirrel (Aug 22, 2011)

kimcmich said:


> Fungus gnats are ... largely harmless.


Actually, the larvae feed on plant roots, so they are very harmful, especially to delicate miniature plants which I grow.




kimcmich said:


> Pinguicula sp (butterworts) are carnivorous plants that work like natural (and very effective) fly paper.


I have gone a similar route, in that I ordered some Drosera species to add to my grow tank (hopefully they will be close to as effective as Pings)

Thanks for your suggestions


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## flyingSquirrel (Aug 22, 2011)

nyskiffie said:


> No other animals in the tank? Can you do a CO2 bomb?


THANK YOU! This is a brilliant idea. I am not sure how I didn't think of it. I doubt if it will get the larvae, and especially not the eggs, but it's worth a try.


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## kimcmich (Jan 17, 2016)

@FS,

I'm a big fan of CO2 bombs (I used them to get rid of a slug problem) - but be advised they are *not* as harmless to plants as is generally believed.

After having done ~15 of them, I have found that certain orchids and, of all things, bromeliads can experience damage. I think the mechanism is acidification of the water sitting on the leaves. A nearly pure CO2 atmosphere will turn into carbonic acid HCO3 when it diffuses into water. This either directly damages leaves or makes them more sensitive to sunburn or attack by pathogens.

I my case, the small Lepanthes and Barbosellas experienced massive leaf loss and several Bromelaids got bleached spots on their leaves. I've experience this several times and the damage is always acute and immediate...

...and I should also say that, while effective at eliminating my slugs, even the longest CO2 bomb I used, that damaged some plants, did not kill the fly larva/eggs of a larger species of fungus gnat. The adults were all killed and some larvae died, too - but some recovered after looking dead and new flies were emerging again 12 hours later.

Oddly, 10 species of filmy ferns and a bunch of others small ferns, mosses and orchids were _not _ damaged at all. Clearly the sensitivity to ill-effects from CO2 are hard to predict just looking at the plants involved...

Edit: I should also add that in my case, even though the CO2 was very effective against slugs, it did not eliminate flies/gnats. Even my longest treatment that damaged plants did not seem to effect fly larvae and eggs. All adults were killed, but many larvae recovered after I cleared the CO2 and new adults started emerging ~12 hours later.


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