Dog Health & CareDog Stories

Natural Fly Killer – A Zip Lock Bag of Water

With summer coming around the corner, the fly is standing in line to attack  everything that does not move, especially our dog. The natural fly killer is something we prefer more than a commercial fly killer, and are always looking for something that works to get rid of each and every fly within range of the dog kennels, patio, yard and inside the house. However, something we never knew existed was the  zip lock bag of water as an indoor fly killer and an outdoor fly killer. Not too long ago we received an email about a popular natural fly killer that costs about four cents – depending on where you shop. After that,  it is history with the zip lock bag and a natural fly killer for our dog.

A zip lock bag of water as a natural fly killer?

At first, we were very skeptical of the idea of a zip lock bag of water used as a natural fly killer. Especially one that would cause flies to run for cover at such a low cost. But we thought to ourselves, “Why not?” With every rescue dog fighting them every summer, we felt a zip lock bag of water for an easy and natural fly killer was something we could afford and was safe for our dogs.  After all, we were not going to be out much for 4 cents if it did not work.

Photograph by Nancy L. Young-Houser
Photograph by Nancy L. Young-Houser

In the kitchen we hung three half-filled zip lock bags of water, with four pennies in each bag. There. We had our natural fly killer up  and were waiting for the flies to land — somewhere but on the dog waiting patiently below the zip lock bag to see what would happen next.

We had tied the closed bags with a twine and hung them (with most of the air removed) in varied corners in the kitchen, porch and outside patio. Within one hour, over 3/4 of the flies were gone. How it happened, we do not know. But try it yourself….do not take our word for it. You will be surprised. There are lots of natural fly killer methods out there, but none are as cheap as the zip lock bag filled with water and four shiny pennies at the bottom!


We went with some out of town friends to Sweety Pies on Sunday for breakfast, and we sat in the enclosed patio section beside the house. We happened to notice a couple of zip lock baggies pinned to a post and a wall. The bags were half filled with water, each contained 4 pennies, and they were zipped shut. Naturally we were curious!

Ms. Sweety told us that these baggies kept the flies away! So naturally we were even more curious! We actually watched some flies come in the open window, stand around on the window sill, and then fly out again. And there were no flies in the eating area! This morning I checked this out on Goggle. Below are comments on this fly control idea. I’m now a believer! ~ Deb


Many people swear that a zip-lock bag filled half-way with water and attached over entry-ways will repel flies. No one yet knows how or why it works, but there is speculation that it has something to do with the way the moving water refracts light. If you have tried this please use the comments form at the bottom of the page to share your results with the rest of us. ~ Sue

October 5th, 2008

I did tried the ziplock bag and pennies this weekend. I have a horse trailer with full LQ. The flys were very bad this weekend while I was camping. I put the baggie with pennies above the door of the LQ. NOT ONE FLY came in the trailer. The horse trailer part had many… Not sure why it works but it does!!!!!!! ~ Ann

September 20th, 2008

Fill a zip lock bag with water and 5 or 6 pennies and hang it in the problem area. In my case it was a particular window in my home. It had a slight but significant passage way for insects.Every since I have done that, it has kept flies and wasps away. Some say, that wasps and flies mistake the bag for some sort of other insect nest and are threatened by this. ~  Danielle

June 7th, 2009

I swear by the plastic bag of water trick I have them on side porch ( our house entry) and all around the basement door. We saw these in Northeast Mo at an Amish grocery store & have used them since. They say it works because a fly sees a reflection & won’t come around. ~ Maggie

May 16th, 2009

Regarding the science behind zip log bags of water? My research found that each of the millions of molecules of water presents its own prism effect and given that flies have a lot of eyes, to them it’s like a zillion disco balls reflecting light, colors and movement in a dizzying manner.

When you figure that flies are basically prey for many other bugs, animals, birds, etc., they simply won’t take the risk of being around that much perceived action. I moved to a rural area and thought these “hillbillies” were just yanking my city boy chain but I tried it, worked immediately! We went from hundreds of flies to seeing the occasional one, but he don’t hang around long. ~ Just DJ
(Submitted by Peggy Winter of Overton, NE)


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  1. Debra St Louis
    November 22, 2017 at 7:31 pm — Reply

    This really works have them in my house and outside hanging on the gate and don’t see flies.. Once in a blue one come from somewhere and sneak inside but when it goes near my computer where I have a bag hanging it runs and then I have my spray and I hit one time with the spray and bam it is dead.

    Also if you have the recycle garbage cans hang one over it..


  2. Michelle
    August 6, 2017 at 12:27 am — Reply

    Flies are everywhere. Getting into my dogs food and creating maggots. So disgusting. I’m giving this a try tonight. I put up 2 bags, one in my kitchen window and one hanging on my deck attached to my umbrella.

  3. putra
    June 28, 2017 at 10:31 am — Reply

    We’ve try it here in tropical Indonesia, with no pennies attached.
    And it’s still get the job done.

  4. December 13, 2016 at 1:31 am — Reply

    The Zip Lock Bag of Water is terrible!

    • Dawn Raye McMannis
      August 10, 2017 at 1:54 pm — Reply

      It’s not working for me either on our porch there’s no sun lite

  5. Cynthia M
    August 15, 2016 at 8:10 pm — Reply

    This works because the water acts as a magnifier. I think the coins assist in creating the mirror. The fly sees itself but magnified and it thinks there are giants there. So it flies away in fear! True!

  6. cheryl
    May 28, 2016 at 1:37 pm — Reply

    At our family reunion three or four years ago, we started doing this at entrances of the bldg & above food. It really works! Before, flies would come in and swarm around the food in droves, but not now!

  7. arlene
    April 26, 2016 at 11:29 pm — Reply

    does this work on bees too?

  8. Malika
    September 7, 2015 at 8:06 am — Reply

    I live in Morocco and have tons of flies in the summer. I’m trying this as we speak. I’ll let you know how it goes.

  9. Laura M
    August 4, 2015 at 2:17 pm — Reply

    I have pennies in a water-filled bag around my dog kennels, and front porch, in several places, and so far no results. Flies are still hanging around having a good ol’ time being annoying, chewing on my dogs ears, buzzing around, biting me, etc. I may alter my bags, amount of water, number of pennies, or locations. Not sure it’ll change or not. Hoping it will.

  10. John
    May 18, 2015 at 5:26 am — Reply

    I tried the bag of water & 4 pennies tied to my front door area. Within minutes no flies.

  11. Michelle Cole
    February 21, 2015 at 8:21 pm — Reply

    I read this from a facebook post a couple years ago about how to a Ziploc bag with approximately 4 in pennies it and have it 1/2 filled with water would repel flies. During that time the flies were bad in my house, I used fly catcher sticky tape and they were still bad .. it drove me crazy to the point I had a fly swatter in my hand most of the day swatting flies. I do not like flies or other bugs in my house so when I read the post I decided to try it to see if it would actually work and Lo and Behold as soon as put one up at each entrance it was like the flies have completely vanished!!! I was absolutely amazed that it worked and the fact is it is very cost effective. Since then I have had no problems with flies although there is one or two that manage to get passed and into the house but not very often I see a fly or flies in the house. I now keep a bag at both entrances to the house and am very happy there are no flies in my house:) Who ever came up with this idea has came up with an Excellent idea to repel flies THANK YOU !!!! I now tell my friends to try it as well as my family It Does Work !!!

    • carolyn baker
      May 11, 2017 at 3:14 pm — Reply

      I also add a little salt and some lemon juice it keeps the pennies bright

  12. DeeDee McFly
    January 16, 2015 at 11:15 pm — Reply

    I’m bangin the bags up now . Dem flys are a gonna be long gone sooooon!!!!

  13. JockM
    December 1, 2014 at 5:53 pm — Reply

    It would be interesting if this would work with plastic PET soda bottles.
    I guess you could bend the pennies to fit in the opening, then hang the bottles around the place.
    I also live in Australia, with no copper pennies – I will give this a try, if I happen to find some.

  14. mark & april
    October 19, 2014 at 10:37 am — Reply

    My mom told me about this and I thought well why not. With the flys so bad this fall on my front porch it coundnt hurt. ¢5 later and the flys buzz the porch but only come within 3 feet of it and turn tail and run. With two bags over the porch not even in direct sun its about 70% less annoyance now. Going to put some all around the back yard now too help with the dogs getting bitten up.

  15. sherri
    August 7, 2014 at 6:56 pm — Reply

    My family and I hung sandwich size Ziploc bags over all our Windows and doors and it worked! We saw this technique in a restaurant. I had now idea about using tin foil or pennies. So, it seems that it worked without either technique. Have a blessed day!

  16. dawn
    July 22, 2014 at 3:26 pm — Reply

    okay well I tried this and it don’t work at all it doesn’t bother our flies they land on the bag and everything oh and the soap and water thing doesn’t work either

  17. Bev
    July 21, 2014 at 5:57 pm — Reply

    I used a bag of water and one penny today and it worked. We were outside eating and being pestered by flies. I rembered seeing the bags in Greece over the doors in restaurants. I put one up and in a matter of minutes, there were no flies. I am convinced.

  18. Lake girl
    July 18, 2014 at 11:30 pm — Reply

    I live in central Alabama and around here a natural predator of flies are hornets. If you have seen a hornets nest it is a gray color and made up of chewed up paper. Anytime a fly sees a hornets nest they go they other way. The ziplock bag resembles a hornets nest therefore the fly leaves. We have used this trick for years down here and it works well.

  19. June 7, 2014 at 11:44 am — Reply

    The problem with this method is that it keeps them away for mere seconds and the flies still exists. They need to be exterminated so that you won’t have to hang these gaudy bags all over the place.

    The very best fly repellent on the market is QuickBayt Fly Bait. They are red sugar granules that you can place on a plate that will attract the flies. It takes about 20 seconds for the fly to start spazzing out from the time they ingest the bait. They are dead within 60 seconds. The eliminate the flies, not just scare them off.

    Here is the cheapest source for the QuickBayt:

  20. wshiwsnt
    May 7, 2014 at 7:33 am — Reply

    it doesn’t kill them-it repels them. reflection of pennies in the water repels them.

  21. Mary
    December 1, 2013 at 8:34 pm — Reply

    This really works!!

  22. Kathy
    August 4, 2013 at 9:07 pm — Reply

    It works! Just had hardwood floors put in and we had to leave the doors wide open for the workers and not one fly in!

  23. Kenneth
    July 19, 2013 at 11:17 am — Reply

    Have tried this, Nebraska flies must be different, does not work!!!

  24. RoadHogs
    July 10, 2013 at 1:10 pm — Reply

    Does this work with misquitoes as well?????????????????????????????

  25. Lisa
    June 16, 2013 at 5:59 pm — Reply

    I just moved to a new house with a lot of fruit
    Trees and the flies were bad. I hung two bags
    In two different spots. The flies are still here but
    Not as bad!
    I live this bag-I-penny thing!

  26. Mikki
    May 26, 2013 at 6:22 pm — Reply

    I recently remodeled our patio and have lovely flowers and water features that are so relaxing, never being able to use the outdoor room because of flies that come into the house. I have had a bag of water with pennies hanging on the patio and in the garage at the kitchen entrance and have not had 1 fly in the house since and it’s a miracle. Im not a fan of bugs, so this is fantastic. 2 months and no flies.

  27. Brian
    May 18, 2013 at 11:00 pm — Reply

    I tried this, if fact I hung several on my patio abouve the table, while the flies did not just disappear they may have been reduced…IDK…the verdict is not in yet on this “fly killer”.

  28. Sandy Welte
    April 20, 2013 at 1:23 pm — Reply

    I haven’t used it at our place yet, but out west we saw them all the time out in the Sturgis area during bike week and asked what the bags for used for!! There were no flies!!

  29. March 25, 2013 at 9:15 pm — Reply

    Can you use glass? Trying to make it look like a unique decoration instead of a random bag of water and pennies.
    For the same reason, could you use colored water?

  30. Jeniffer Sterland
    March 2, 2013 at 8:05 pm — Reply

    This is intriguing. Summer in Australia is a Great Convention for Flies! I’m just wondering what sort of coins I should use. I think I might have a couple of old Stirling-coinage pennies [copper], but where have I hoarded them … mmm?? When Decimal Currency arrived in Australia in 1964-5 we switched to ‘silver’ coins; 5 cent, 10 cent and 20 cent coins, with a later addition of a 50 cent coin. These are not actually silver. As the bag is sealed, I guess it is only a matter of light reflection, as no ‘odour’ would be released. I’ll see how I get on and report back, just in case there are other Aussie readers here. Or I would appreciate hearing from them if they’ve tried the idea.

    • May 25, 2014 at 10:38 pm — Reply

      Hello, will send you some American Pennies if the Aussie currency doesn’t work, am curious if it will work on Aussie flies.

    • June 1, 2014 at 3:15 pm — Reply

      I need your address

  31. Marifel Baez
    August 27, 2012 at 9:45 am — Reply

    Accordig to my parents it has to do with their eyes, they have not one but thousands of mini eyes and those cant take the water/light effect in the bag. (We didnt use pennies)

  32. July 30, 2012 at 6:59 pm — Reply

    we have bag of water with a few pennies over our front door outside the flies still hang out on the screen so i don’t think it is helping we even have one of those sticky fly strips hanging in the garage has a few flies on it the rest of the flies i think ignore it i know they are bad this yr we live in ohio

  33. john hebert
    July 3, 2012 at 4:14 pm — Reply

    Copper (penny), or silver (old coins) are both fantastic disinfectants. Algae cannot grow due to the metals dissolved in the water. I imagine that was the idea there. I’m using a couple crumbled up pieces of foil for reflection. Never heard of just water, but I haven’t had a fly in my house in days. I have 4 dogs and 2 cats. The house isn’t terrible, but if I drop food on the floor, I probably wouldn’t eat it. And still, NO FLIES. Not even in the bathroom, where they usually seemed to congregate. It works for some reason, probably an optical thing is my best guess.

    • Rick Love
      July 9, 2013 at 4:40 pm — Reply

      Thanks John

  34. Matt :P
    June 23, 2012 at 8:36 pm — Reply

    The penny inside the bag HAS to be shiny, only because when the water makes the penny looks bigger because of magnification, the shiny-ness of the penny makes the fly scared because it makes the fly think it is bigger then them and they fly away. I learned this from a pastor from up the street from me 🙂

  35. Rebecca
    June 3, 2012 at 7:44 am — Reply

    This works, a bug guy told me that the reflection of the bag and movement messes with the flies compound eyes and freaks them out.
    The pennies are in there to keep the water from molding.
    Usually they use silver coins but probably people might decide they want that coin.
    So, pennies are cheaper.
    Also, if you have a fan above tables or blowing from some side source, that keeps flies, mosquitoes, wasps and bees away because they don’t like to try to fly in the wind.
    The fog sprinklers also work but people at the tables get wet from all of the mist.
    When we have a party, I first spray the perimeter with the bug fog that drives them away. Then we put 2-3 fans blowing hard in the yard pointed at the decking and that helps a lot keeping especially the mosquitoes away.

  36. Rochelle
    June 2, 2012 at 10:27 pm — Reply

    In my country it is done a lot. You don’t even need to put penny’s in de bags, just water works also. It is said that when the flies look at the bag with water, they will see a huge reflection of themselfs. This is whats scares them away.

  37. bud W
    May 23, 2012 at 7:38 am — Reply

    Flies are near bottom of the insect food chain and as such they are trying to avoid anything that reminds them of a larger preditor. Most of the preditors have large protruding eyes. So large shinney pennies reflecting a prizom of light is an easy explaination of why this works. I live on a boat and believe it or not I have no fly zone aboard the boat. It does not catch them. however they tend to stay clear of the area.

  38. Debbie C
    May 5, 2012 at 10:49 am — Reply

    We came home to a full house if flies, someone told us to do this but leave the bag open & it would catch them…needless to say, 4 days later…nothing & house still full of flies

    • Cecelia
      May 22, 2012 at 12:25 pm — Reply

      I think it is supposed to drive them away from the bag, not toward it to be caught.
      Also, was the room well-lit, to where (if it really works by light), the light would be able to shine through the bag? (maybe the color of the light matters, like white light from outside (or an LED) is better than just yellow light from a lightbulb. Was it hanging up? How did you manage to hang it up but leave it open?

  39. Donna
    September 11, 2011 at 7:21 pm — Reply

    We thought the plastic bag fly thing was just a joke to see how many people would do it. Well, we were camping on Lake Superior and lots of flys….lots. I remembered about the plastic bags and made four and attached them around our tent awning. NO MORE FLIES!!!! I am not kidding…and Northern Michigan flies are the toughest! We camped for 2 weeks and no flies.

  40. nostoc
    July 4, 2011 at 6:49 pm — Reply

    I was, and I guess still am, a doubter. We have a large family reunion every July 4 in a city park pavilion. With dozens of covered plates from just as many kitchens, you can imagine a hot summer day in Southeast Kansas becomes fly haven every year. This year I put up bags of water on three sides of the open pavilion. During the meal you could count the flies we saw on one hand. A couple hours later there seemed to be a couple dozen buzzing around the floor, but none on the tables or near the food. I suppose the refracted llight was not visible from the floor under tables. I still think this could be coincidence, but none of us remember a single year when we saw so few fliles. We’ll probably disprove this theory by trying it the next few years. However, if we go twp or three in a row, we might be convinced this thing works.

  41. lavonna
    September 13, 2010 at 8:57 pm — Reply

    I don’t know what it is but i have been seeing these bags all over and didn’t want to seem dumb so i never asked why, until Labor day weekend. My family and I went to a BBQ which lasted all night. Needless to say flies and BBQ’s go hand and hand. I tell you we stayed outdoors until around 2am not one fly. I said WTF. Of course i now have bags at every entryway to my house. It’s to bad I had to find out the secret in Sept.

  42. Criss
    August 31, 2010 at 7:28 am — Reply

    We’ve recently purchased a few acres in Farmersville TX and every outbuilding had old plastic bags hanging from string I knew there must have been something in them to repel flying insects because the property was previously used for boarding horses. I was pleasantly surprised to find it was just plain water and am in the process of replacing the old bags with new bags filled with water the only problem is in the low ceiling buildings like the chicken coop where our recently rescued Anatolian Shepherd likes to jump up and bite the bags. My son suggested using mini disco balls and I was wondering if anyone has tried using disco balls in place of the bags of water.

  43. ken
    August 21, 2010 at 7:33 pm — Reply

    i Gila Bend,Az in the dead of summer we stopped at an ice cream shop that had i plastic i gallon jugs hanging near the picture windows that surrounded the serving area.there was not a fly in the place.when asked the owner told us they had used this method for many,many years.this was 23 years ago.i have i gallon jugs hanging around my donkeys open pen.guess flies.dont know just works.

  44. jpdaigle
    May 31, 2010 at 7:37 pm — Reply

    also its a good time for for me to try it

  45. jpdaigle
    May 31, 2010 at 7:36 pm — Reply

    i seen this in victoria Tx at a resturaunt but i didnot know about the pennies so i will try it with pennies

    September 27, 2009 at 7:46 am — Reply

    I vacation in Myrtle Beach,SC for over 50yrs now.I first saw this at a diner about 15 yrs ago.The bags are still there.I guess it works.I don’t remember seeing any flies anywhere.
    ART H.

  47. […] We tried the bag of water with four pennies we had written in our previous article, “A Ziplock Bag of Water and Four Pennies = No Flies“  which works well inside a closed area but not good for large areas or […]

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