Do I need a permit to use algaecide or herbicide in my pond in Pennsylvania?

The rule. Before any herbicide, algaecide or fish-control chemical goes into surface water in Pennsylvania, including a private pond, you need a joint DEP/PFBC "Chapter 91" permit. There is no minimum amount: any use needs it, and use may not start until the approval arrives. Apply on form 3800-PM-BCW0094b, one application per site (a tax parcel or contiguous parcels, up to 20 water bodies). For ponds and lakes the application goes to DEP only, by upload or mail. DEP usually issues the permit to the person who owns or manages the property. Permits are typically issued without an expiration date; changing the water bodies, the product or a higher dose or more treatments needs a new application. Application fees: $250 new, $250 renewal, $100 amendment, $50 transfer; no annual fee.

Checked Oct 4, 2026 · Source: Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #2, #3, #8, #10, #11, #28, #29 This may be outdated

Most pond owners don't know it. In Penn State surveys, about 40% of pond owners with nuisance algae and plants had used aquatic herbicides, and 65% of those owners did not know a state permit is needed before any herbicide goes into a private pond or lake.

Checked Oct 4, 2026 · Source: Permit Requirement for Use of an Aquatic Herbicide in Ponds (updated Sep 8, 2025) This may be outdated

What the application asks for. The pond's name and location, with a topographic map (pond circled and named) or its latitude and longitude; how the pond is used and which fish live in it; the pond's total area, the area you'll treat and the average depth; the plant or algae you want to control; each product's brand and manufacturer; the dose and the number of treatments a year, from the label. Only products registered with the U.S. Environmental Protection Agency and with the Pennsylvania Department of Agriculture, and labeled specifically for aquatic use, can be listed on the Chapter 91 permit application. DEP's pesticide-permit FAQ states that submissions must include a PNDI environmental review receipt, which you get by screening the site in PA Conservation Explorer. Check the application instructions for your permit type. Measure first with the pond size calculator and name the plant with the plant guide.

Checked Oct 4, 2026 · Sources: Permit Requirement for Use of an Aquatic Herbicide in Ponds (updated Sep 8, 2025); Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #14 This may be outdated

Pond dyes, alum and other additives. A pond dye used to control algae or plants (for example by blocking light) needs the joint Chapter 91 permit like any other chemical. A dye used only for color does not, and in a pond fed only by runoff or groundwater it may be applied according to the label. But if a stream flows into the pond and water flows out, dyes and other products that change the water's appearance generally may not be used unless DEP authorizes it. Alum or any other chemical used to control algae also needs the joint Chapter 91 permit. Enzyme products could be treated as chemicals under Chapter 91; DEP asks you to contact its Bureau of Clean Water about your product.

Checked Oct 4, 2026 · Source: Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #23 and #24 This may be outdated

Hiring an applicator. A business that applies pesticides for others must hold a Pennsylvania Department of Agriculture pesticide application business license, renewed every year with a $35 fee, and must employ at least one certified applicator in each category it works in. Aquatic work falls under business category D (Aquatic Pest Control), applicator category 09. PDA publishes a public search of licensed businesses by category and county. Ask who will file the permit: DEP usually issues the permit to the person who owns or manages the property, not to the person who applies the product.

Checked Oct 4, 2026 · Sources: Pesticide Application Businesses; Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #2, #3, #8, #10, #11, #28, #29 This may be outdated

Large lakes. A separate NPDES permit for weed and algae control applies only at large scale: treating at least 80 acres of water, or at least 20 continuous linear miles at the water's edge, in a calendar year. Below those thresholds, use is automatically covered by DEP's PAG-15 general permit with no application, but the joint Chapter 91 permit is still required. Above them, DEP wants the Notice of Intent or permit application at least 30 days before the threshold is exceeded. The current PAG-15 took effect October 29, 2023 and expires October 28, 2028.

Checked Oct 4, 2026 · Source: Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #1, #2, #7, #8, #20 This may be outdated

Plants standing in a wetland. DEP counts wetlands, including seasonal ones, as surface waters, so treating plants standing in a wetland or in water needs this permit too.

Checked Oct 4, 2026 · Source: Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #2, #3, #8, #10, #11, #28, #29 This may be outdated

Protect your fish. Killing a lot of plants or algae at once can crash the pond's oxygen: PFBC says lack of oxygen from decaying plants is the most common cause of fish kills in treated ponds. Penn State advises treating early in the growing season and, where a lot of vegetation must be treated, doing a third to a half of the pond at a time with one to two weeks between treatments. The product label still controls.

Checked Oct 4, 2026 · Source: Pond Management (FAQ: controlling submerged vegetation) This may be outdated

Options that don't need this permit. Netting, raking and skimming. Barley straw: Barley straw needs no permit (PFBC); it prevents algae rather than killing it. Grass carp, which need their own PFBC permit: PFBC grass carp permit needed for each waterbody before buying or stocking; $85 fee, returned if denied. And for the long run: Weeds and algae are a nutrient problem first: buffers, septic care and less fertilizer (Penn State).

Checked Oct 4, 2026 · Sources: Pond Management (FAQ: How can I control algae?); 58 Pa. Code § 71a.10, Triploid grass carp; Filamentous Algae (updated May 19, 2025) and the companion Penn State plant fact sheets This may be outdated