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Physan 20 Concentrate by Physan 20
Physan 20
Physan 20 Concentrate

PHYSAN 20 is a broad range disinfectant, fungicide, virucide, and algaecide which effectively controls a wide variety of pathogens on hard surfaces and plants. Its applications include greenhouses, hard surfaces, lawn and turfgrass, seedlings and cut flowers, decorative fountains, pools and birdbaths, and plants.

Physan 20 Greenhouse Disinfectant can be used in a variety of hydroponic applications to:

  • Prevent the development of disease
  • Kill algae that may form on system surfaces and substrates

Please remember that Physan 20 is a liquid concentrate, which must be extensively diluted for hydroponic applications. This means that in some cases, only a drop or two of the concentrate will be required in a volume of water to create the correct dilution. Do not be tempted to use more Physan 20 than directed and always measure when mixing. NEVER estimate by eye the amount you add to water.

Cleaning Hydroponic Systems Between Crops

Physan is an excellent product to use to clean and disinfect your entire system between crops. Physan can be used on plastics, metal, and glass surfaces, and is safe to run through delicate pumps and meshes.


Product Details
Recommended Usage
  • Physan 20 Application Guide
  • Physan 20 Commercial Label
  • Physan 20 Home & Gardening Label
  • Physan 20 SDS
Use & Instructions

TO USE: Mix 1 Tablespoon Physan 20 in a gallon of water to create a disinfecting solution. This may be used to apply directly to hard surfaces via a spray bottle or clean sponge. The wet surface should be scrubbed if visible dirt or algae are present. Make sure the surface remains wet for 10 minutes to ensure killing of all organisms Physan 20 is capable of killing. You may also run this dilution through your hydroponic system to clean and disinfect it.

Physan 20 contains a foaming agent. At this dilution, you may notice foaming if you run the product through your system and you run aeration. This foam is harmless. If it is particularly bothersome to you, you may add a commercially available de-foaming agent.

Please note: The Physan 20 instruction booklets state that Physan should not be used in “irrigation systems”. This wording refers only to OPEN irrigation systems that dump water that might be treated with Physan 20 into ponds, lakes, or any fish bearing water. Physan 20 is toxic to fish. It coats their gills and interferes with their breathing. This wording is provided by the U.S. EPA and we are not permitted to change it. However, hydroponic systems are considered CLOSED irrigation systems that do not endanger fish. Physan 20 can be used in this closed system.

Algae Control on Rock Wool and other Substrates

Physan 20 can be used to treat rock wool and other growing substrates to eliminate algae both between crops and in the presence of plants. You must use different dilutions for each of these applications.

TO USE ON ROCK WOOL/SUBSTRATES BETWEEN CROPS TO TREAT ALGAE: Make a dilute solution by adding 1 Tablespoon of Physan 20 to a gallon of water. Soak the cubes in this solution for 10 minutes. Remove cubes and let dry. Do NOT plant in the cubes for 7 days. This allows for a complete kill of algae and a breakdown of the Physan 20 active ingredients so that tender plants are not harmed upon planting.

TO USE ON ROCK WOOL/SUBSTRATES ALREADY PLANTED TO TREAT ALGAE: Make a dilute solution by adding 1-1/2 teaspoons of Physan 20 to a gallon of water. Put in a sprayer bottle and spray the surface of the rock wool substrate where algae is present. Let the sprayed surface remain wet for 10 minutes. You may also use this same dilution to spray the entire plant as well as the affected surfaces for complete pathogen control. If algae persists, apply again in same manner in 7 days. Measure carefully and DO NOT increase the concentration of the Physan, as crop damage can occur.

Adding Physan 20 to Nutrient Solutions

Adding Physan 20 to organic nutrient solutions may reduce or negate completely the algae and pathogen-killing capabilities of Physan 20. As Physan 20 is pH neutral, its addition will not change the pH of the nutrient solution. However, it should be considered that tender root systems are potentially at risk from a continual bath of Physan 20 solution. Because we cannot know what type of plants you are growing and what nutrients are being used, we can give no guidance as to the combining of Physan 20 with nutrients.

Physan 20 as a Foliar Spray for Pathogen Control

Physan 20 can be applied to plants as a foliar spray to control pathogens. However, it is NOT an insecticide and will not kill aphids, mites, scale, or pests of this sort. Physan 20 leaves no harmful residue if foliage is dried and smoked.

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