FlytrapCare Carnivorous Plant Forums

I do believe I have a moderate to heavy fungus gnat infestation among my pots (see supporting evidence below).

I've got some seedlings, some sundews, flytraps, and sarrs thats seem to be growing ever so slowly. I'm wondering if it's fungus gnats causing the slow growth or not. Without a doubt, though, there are fungus gnats present. My older sundews seem to be enjoying the gnats and even the small seedlings seem to be getting one every now and then.

I used some water this past winter that I steeped some crushed mosquito dunk in. I may have overdid it...basically a heaping tablespoon to a gallon that had steeped for a couple of days. When I checked the TDS of the drain water from the pots it was really high. Now, maybe it was something else, maybe I hadn't checked it for a while, maybe I hadn't topwatered in a while...I dunno. I need to pay better attention. Or, maybe it was just too much mosquito dunk in the gallon of water. But, heck, I don't even know if mosquito dunk can raise the TDS of water...

So, tonight I took a gallon of some really nice and fresh 1ppm rainwater and added a good "pinch" of crushed up mosquito dunk to it...probably around a teaspoon of it. I shook the jug good and will let it steep over night and check the TDS in the morning...and then again tomorrow night to see what the TDS reading is.

I'm curious if anybody has noticed a rise in the TDS reading of water treated with the dunks. Also, if you're only treating a couple of gallons of water to be used for fungus gnat treatment how much have you found effective? How long did you let it steep before using it?

Thanks, as usual, for the feedback!!!

People have said they raise the TDS. They are just a media for a live bacteria so i don't think it would bother plants. I have never had a issue, i use 1/2 for a pool and 1/4 for smaller tubs. My TDS always stays low in the summer when i use the dunks because of my floating plants.

For mosquitoes the instructions for the dunks say they will cover 100 square feet of water surface. I've been using 1/4 of a dunk in the garbage cans. But, there's only 5 square feet of water surface there, so I'm probably overdosing it for mosquitoes. Those are back-up/emergency storage containers which I seldom use. Most of my other water is stored in covered buckets or jugs, so no issues with mosquitoes.

BUT, it appears fungus gnats are another issue altogether! I need to figure out a good recipe to use "per gallon milk jug" which are my usual storage and watering containers. Some things that I found while surfing the Internet:

> Soak a dunk in a gallon of water overnight, dip out the dunk and save it to use again.
> Use 4 tablespoons of bits per gallon, soak overnight, and skim off the bits to use again.
> Crush a dunk and soak 1/4 to 1/2 of it in a gallon of water overnight, skim and use again.
> etc.,.

It seems that the standard recommendation is an overnight soak of from 1/4 to an entire dunk in a gallon of water. I can't see it doing any harm in going with a full dunk, it just will be more bacteria released overnight into the water which seems would be a good thing. Or, maybe use a full dunk for two gallons...making two gallons would be more efficient for my needs. It was also stated somewhere to use the dunk infused water within two days. I figure putting the used dunk in a ziplock and putting in the refrigerator would be a good storage tactic. I didn't find anywhere that mentioned how many "reuses" a dunk is capable of providing, though.

So, my "pinch" of dunk that I put in the gallon last night might be woefully inadequate. I'll be checking the TDS today, with the possibility of the TDS rising sharply one of my initial concerns. But, equally important is to get the fungus gnats under control. Something's gotta give!

Roughly 16 hours after putting the "pinch" of crushed up mosquito dunk into a gallon of 1ppm rainwater I get a 28ppm reading on my meter. That's a pretty large swing for just a small amount (maybe a teaspoon) of the dunk in a gallon.

Before I took the meter reading I put a whole dunk in a 2.5 gallon bucket of 2ppm water. I think I'm going to let it go until this evening and then check it to see if it is already risen.

So, I'm thinking of going ahead and using the gallon from last night. It is well below 50ppm at the moment but once it comes out the drains it'll probably be well above 50ppm.

Well now, it just dawned on me...there's probably a 15F degree difference in temperatures between last night and this afternoon so I got to thinking that the actual TDS reading may not have risen as much as I think. I did a test a few months back where I measured the difference in TDS measurements for different waters at different temperatures. Looking at it, with a low PPM water such as I'm using, the temperature difference shouldn't have made much difference at all. So, the rise in TDS must be "real".

Data from the temp/water/TDS test post429141.html#p429141 :

Tap water (from my hi-tech kitchen sink)
Temp 58F TDS 300ppm
Temp 82F TDS 396ppm
Temp 90F TDS 424ppm

Stored rain water
Temp 52F TDS 9ppm
Temp 82F TDS 14ppm
Temp 90F TDS 16ppm

Fresh rain water
Temp 48F TDS 2ppm
Temp 80F TDS 3ppm
Temp 91F TDS 4ppm

I've had some things going on and I haven't used any of the mosquito dunk water yet.

Checking this afternoon here's the TDS readings...

The gallon jug with the pinch in it increased from 28ppm to 33ppm. That's not too bad, maybe it's leveling out.

The 2-1/2 gallon bucketful that I put the whole dunk in yesterday rocketed up to 45ppm. I took the dunk out and will see if any residual dunk in the bucket increases the TDS even more.

Of course the question is...how much dunk/bacteria do you need in the water for it to be effective against the gnats?

I checked the jug and bucket tonight. Temperature was a bit cooler than when I checked yesterday...

Gallon milk jug with a pinch of dunk in it: 29ppm
2-1/2 gallon bucket full that I removed the dunk from: 44ppm

So basically not much different. The question is whether the gallon with a pinch in it and at 29ppm (started with 1ppm water) has enough bacteria in it to be effective against fungus gnat larvae?