Hydrothol® Granular Aquatic Algaecide & Herbicide

Works on Both Weeds & Algae


Cannot be shipped to: AK, CA, CT, DC, DE, HI, MA, ME, NJ, NY, PR, RI, VT, WA or Canada

  • 530362 - 20 Pounds
  • $119.99
  • 2+ 20lb Bags - $114.99 Each
  • Fast-Acting Granular Formula
  • Great For Bottom Growing Algae & Chara
  • Control Weeds Surrounding Docks & Shorelines

Hydrothol® Granular algaecide and herbicide for ponds provides rapid-acting contact control for submerged weeds and algae. Hydrothol even works where there is moving water such as a canal or bay area. Hydrothol® can be used in combination, in rotation or as an alternative to copper for control of algae. Dosage rates vary depending on what type of algae or weed is being treated and the density of the infestation.

Tech Specs

Usage Information

Hydrothol Granular Algaecide 20 Pound
20 Pound
Application Granular
Temperature Restriction None
Square Footage Per Container Up to 8,000 Square Feet
Shelf Life 5 Years

Dosage Rates

Treatment Area
Hydrothol To Treat Algae
Hydrothol To Treat Chara
Hydrothol To Treat Weeds*
1,000 Square Feet 2.5 Pounds 5 Pounds 7.5 - 25 Pounds
2,000 Square Feet 5 Pounds 10 Pounds 15 - 50 Pounds
4,000 Square Feet 10 Pounds 20 Pounds 30 - 100 Pounds
8,000 Square Feet 20 Pounds 40 Pounds 60 - 200 Pounds

*Use on aquatic weeds is dependent on weed type and density.

Please note: Above are recommendations. Always read the product label.

How To Apply

Broadcast Hydrothol onto the area to be treated using a granular spreader. Treat only up to half of the pond's surface and wait 10-14 days before a second treatment. During hot weather or when treating heavy growth, it is important to treat no more than ¼ of your pond at a time and wait the full 14 days before re-applying. This helps lower the risk of fish loss during hot weather or when treating heavy growth. Once it is completely dead, use a rake, like the Pond & Beach Rake, to remove dead algae away to prevent an accumulation of dead algae and muck.

When To Apply

Hydrothol should be applied when algae and weeds are actively growing. Begin applications when algae and weeds first appear. Unless steps are taken to reduce the overall nutrients in the pond, multiple applications may be needed for full season algae control.


  • Do not use in ponds with koi, grass carp or goldfish. Not for use in water garden or koi ponds.
  • Do not use in ponds with trout, unless carbonate hardness is above 50ppm.
  • Wait 7-25 days before using treated water for human drinking water.
  • Wait 7-25 days before using treated water for livestock and domestic animal consumption.


Replacement Parts

Here are the replacement parts for Hydrothol ® Granular Aquatic Algaecide & Herbicide.

Weeds Treated

The first step towards effectively treating any pond weed is proper identification. Hydrothol® Granular Aquatic Algaecide & Herbicide is recommended for use against each of the weeds listed below. Click on your desired weed for more information and alternate control options.

  • American Pondweed
  • Chara
  • Coontail
  • Curly Leaf Pondweed
  • Filamentous Algae
  • Hydrilla/Elodea
  • Planktonic Algae
  • Southern Naiad

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