Seasonal care calendar
May pond care in Pennsylvania
Plants are growing fast. If you plan any chemical treatment, early in the season is the safer time, and only with your permit in hand.
- Permit timing
No permit, no treatment: Any herbicide or algaecide in a pond needs a joint DEP/PFBC Chapter 91 permit first, at any amount.
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 Feb 21, 2025), FAQ #2, #3, #8, #10, #11, #28, #29 This may be outdated
- Care
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Checked Oct 4, 2026 · Source: Pond Management (FAQ: controlling submerged vegetation) This may be outdated
- Care
Stocking grass carp? PFBC's older pond-owner guide suggested late spring, when plants start to flourish. Buy only USFWS-certified triploid grass carp from a PFBC-approved dealer; keep the bill of sale.
Checked Oct 4, 2026 · Source: 58 Pa. Code § 71a.10(f), Triploid grass carp: prohibited acts This may be outdated
Source: Pond Owner's Guide to the Use of Triploid Grass Carp in Pennsylvania (6-12)
- Care
Trim grass, weeds, brush and small trees on the dam and banks, but leave large established trees: Penn State says their roots help hold banks and dams.
Source: Winter Pond Inspection Checklist
- Care
Filamentous algae starts on the bottom in shallow water before it floats up as mats. Removing it early by net or rake is easier and takes nutrients out with it.
Source: Filamentous Algae
- Safety
Learn the signs of a harmful algal bloom before the season starts. Suspect a harmful algal bloom? Keep people and pets out and report it to the PA HABs Task Force.
Checked Oct 4, 2026 · Source: Harmful Algal Blooms (HABs hub) This may be outdated
This calendar repeats every year. Permit reminders show the date we last checked the rule.
The Seasonal Pond Letter
Free, four times a year: mid-February, May 1, mid-August and November 1: what to do and file before each season. Sign up.