Diagnosing and Removing Fungus Gnats From Your Hydroponic Garden

Diagnosing and Removing Fungus Gnats From Your Hydroponic Garden

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If you notice tiny gnats flying around your hydroponic garden then you may be having an issue with fungus gnats. Besides seeing these pests fly around, they can be hard to detect until having issues with your plants. While the adult gnats do not harm your garden, their larvae can and will destroy it.

Get To Know The Enemy

Fungus gnats make their way into your hydroponic garden from outside. They can also be brought in from plants that have already been compromised by fungus gnats. They lay their eggs on dead plant matter, algae or the moist environment of your plant’s root system.

How Fungus Gnats Affect The Hydroponic Garden

A fungus gnat can lay a couple hundred eggs at a time. After hatching, the fungus gnat larvae eat away at your plant’s roots, not only damaging the root system but leaving the plant open to viruses and pathogens. If left unchecked, they quickly multiply, taking over your garden.

A plant that is being attacked by fungus gnats will often show signs of various nutrient deficiencies since the plants damaged root systems is being damaged.

How To Determine If You Have Fungus Gnats In Your Hydroponic Garden

You may see fungus gnats flying around your plants or sitting on the leaves. They like to walk around the grow medium and the base of the plant. Their larvae often work below the grow medium so they often go unnoticed for a short time. If you move the grow medium around at the base of your plant and you see gnats, they have gotten into your plant’s root system. If the problem has been going on for a while you might see some larvae moving amongst discolored roots.

You may also see larvae in algae growing on your grow medium or in your reservoir. Try to keep areas clear of sitting algae as much as possible.

How To Prevent Fungus Gnats Problems

The easiest way of preventing a fungus gnat infestations is by keeping them from getting to your hydroponic garden, to begin with. Enclosing your garden is the biggest preventative measure you can take. Any vents to the outside should contain a filter so tiny gnats don’t make it in. If your hydroponic garden is open in your home, make sure window screens are on before leaving the window open and try to not leave the door open for too long.

The second way that gnats can be introduced to your is through clones or transplanted plants that contain eggs or larvae themselves. Double check all plants being brought in for signs of pests.

The gnats are attracted to dead matter and algae. Remove it from your hydroponic immediately when noticed.

Let the top of your plant’s root zone to dry out between waterings or keep the top couple inches of grow medium dry.

How To Save Your Hydroponic Garden From Fungus Gnats

First, you should take away their open food source by removing any dead matter or algae from your garden. I also recommend using Use sticky strips to catch gnats before they lay eggs in your plant’s root zone. You also want to catch the gnat before it dies and becomes food for gnat larvae.

There are a few ways to actually kill the fungus gnat larvae that are in living in the plant’s root system. A couple of them are:

Hydrogen Peroxide

You can use 3% hydrogen peroxide at ~2 teaspoons per gallon to combat fungus gnats and provide some sterilization.  Start plants off at a smaller dose and increase after a week or two. Hydrogen peroxide can also burn your plants and is not my preferred method.

Commercial Products

There are commercial products on the market geared towards hydroponics that will kill the larvae in your hydroponic system. Tanlin is an example of a product that is safe for your garden and can be used up until the day of harvest. It’s easy to use, effective and safe so I believe it can be worth the cost. If you’re worried about losing your garden to fungus gnats it might be worth a shot.


While fungus gnats can be a real headache and even the end of your hydroponic garden, they are a pest that can get gotten rid of and your garden saved. As with all pests, diseases, and deficiencies, diagnosing the problem early gives you the best chances of saving your garden.

2 Answers

  1. Nicole
    November 12, 2019 at 8:26 am

    I can use some advice I’m growing cucumbers for the first timehydroponicslly the leaves are getting yellow spotted I saw a few gnats flying near them . Also after self pollinating the female with the male using a paint brush a day or two later the flower dies on the female is this supposed to happen ?

    1. NoSoilSolutions
      November 13, 2019 at 9:34 pm

      I would first make sure you don’t have a larger fungus gnat problem. Then make sure your pH is correct and do a fresh change of nutrient solution. It could also be that the flowers are not getting pollinated quite enough. It usually takes a few times of hand pollinating for them to be well pollinated.

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