Midge Fly Complete – Eliminates Redworms and Midge Flies In Wastewater



Larva-Zyme helps degrade the cocoons red worms like to build around themselves, exposing more red worms to the AQUABACxt treatment. You can often find these cocoons on the walls of clarifier rings, or the sides of basins. This simple trick can increase the effectiveness of AQUABACxt dramatically.

We recommend using Larva-Zyme for the for the first 20 to 40 days of any treatment. After this initial treatment an annual or biannual 20 day treatment is helpful for restoring the benefits.


AQUABACxt is a highly effective, US EPA-registered biological larvicide. It contains a species of bacteria called bacillus thuringiensis (BT), an approved larvicide for controlling red worms and midge flies in wastewater treatment plants.

Red worms find wastewater plants to be a perfect home. They survive by eating your MLSS, then hatch into midge flies, and the cycle repeats. The active ingredient in AQUABACxt kills the redworms and breaks the cycle.

Common symptoms of red worm infestations include: disappearing MLSS (the red worms are eating it), stringy or clumpy return activated sludge, and nuisance flies that attract pests. AQUABACxt is safe to use and will only kill a very narrow set of target species; larvae of the mosquito, midge flies, and black flies. It will not cause effluent toxicity issues.

*Ask your technical rep for pricing on pallet or tote quantities*

5 Gallon Case of Each


The Science Behind It

AQUABACxt and Larva-Zyme

Larva-Zyme is a catalyst that degrades cocoons, exposing more of the worms to the Aquabac XT treatment. When used alone, we typically see Aquabac XT kill 70 to 90 percent of the redworm population, and dramatically decrease midge fly activity. By adding Larva-Zyme to the treatment, we can typically improve the kill to 100 percent, or very near 100 percent.


  • Wastewater Plants
  • Pond Systems
  • Drain Lines


    • Kills Red Worms and resulting Midge Flies
    • Stops Red Worms from eating MLSS
    • Bacterial Based

Midge Fly Impact on Wastewater


Midge flies, or chironomids (Chironomidae), commonly occur in wastewater treatment plants and pond systems.  The red worm that forms the midge loves the nutrient-rich conditions in a wastewater treatment plant and feeds off bacteria and sludge.  The worms will eat mixed liquor and once transformed into adults, clog filters and buildings entrances.  Some operators have told us they couldn’t see past their hand in some buildings.

Red worms, also called blood worms, are found in mixed liquor.  Over a period of ten days the eggs hatch into red worms and then pass through the pupa stage to become adult midge flies.  With no aquatic life to feed on the midges, their life cycle runs uninterrupted, and they multiply fast. If left alone midge flies will cause poor settling, high TSS, and disrupt the bacterial environment.

*There is no LC50 for aquatic organisms except for mosquito larvae.  All other organisms except nuisance flies and midges Psychoda, Chironomus, and Chironomine are not affected by the product.  Minnows, fish, Daphnia, even other aquatic insects can’t be killed by the active ingredient in the formulation.  AQUABACxt is specific to mosquito, blackfly and midge larvae and again is not toxic to anything in the application sites except the larvae of these targets.  The LC50 against susceptible mosquito larvae averages 0.15 micrograms per milliliter

Not registered for use in the state of New York.


Midge Flies & Red Worms: What You’ll See


Red worms thrive in sludge that builds up below aerators.

Masses of red worms congregating at the bottom of a drained aeration basin.



The coating on this clarifier rake are typical red worm cocoons. When scraped, masses of red worms will emerge.


Disc filter media is one of many spots midge flies can burrow in and multiply.

Case Study – UV Disinfection Room

UV-disinfection-room-cleanChallenge: A 6.5 MGD wastewater treatment plant in Wisconsin was dealing with a UV disinfection room that was always covered in midge flies. The operators were constantly cleaning the room and had installed bug zappers to try and control them. Unfortunately killing the flies did no good as new ones were constantly developing in the clarifiers.

Solution: They began using our AQUABACxt to rid their system of red worms at the source without harming the good bacteria and Larva-Zyme to degrade the protective cocoons.
Results: This combination was very effective and now they have a UV building that’s not a nightmare to spend time in.


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