Koi Pond Builders in Suffolk County, Long Island — APM O'Neill & Sons

Koi Ponds &
Water Features.

Custom koi ponds, pondless waterfalls, ecosystem streams & fountains across Suffolk County. EPDM liner, sized filtration, natural stone builds.

35
Years serving Long Island
Built
for Long Island Winters
4.9
Google review rating
Lic # 58161-H
NY License · Fully insured
What's built in

Details that separate
good work from great.

Four disciplines · One crew
№01

Sized filtration

External bio-filter + skimmer matched to actual fish load — not undersized pond-kit hardware sold to fail.

Included in every build
№02

45-mil EPDM liner

Fish-safe EPDM over geotextile underlayment, seamed and boot-flashed at every penetration.

Included in every build
№03

Natural stone builds

Boulder edges, stone waterfalls, and moss-rock spillways — hand-set, not veneered.

Included in every build
№04

Winter-ready depth

3–4 ft.+ pond depth with de-icer and aerator provisions so koi overwinter safely on Long Island.

Included in every build
Why homeowners choose us

Why hire us
for Koi Pond Builders.

Licensed & insured

Suffolk County HIC License # 58161-H with full liability and workers' comp coverage.

35 years on Long Island

Family-owned and operating across Suffolk County since 1991.

Workmanship warranty

Every installation is backed in writing — base prep, drainage, and finish work included.

Free written estimate

On-site measure and a clear, itemized proposal before any work is scheduled.

The build · Five stages

Five steps. One crew.

A cohesive process engineered for durability and professional delivery.

  1. 01
    The Discovery

    Design consult

    On-site walk — pond vs. pondless, location, sound target, and fish load.

  2. 02
    The Blueprint

    Layout & materials

    Boulder, liner, filtration, and lighting selection confirmed before we dig.

  3. 03
    The Logistics

    Excavation

    Pond hole cut to spec depth with shelves, underlayment and EPDM liner set.

  4. 04
    The Build

    Plumbing & stone

    Skimmer, filter, pump, and lighting plumbed; boulder edges and waterfall hand-set.

  5. 05
    The Standard

    Start-up & handoff

    Fill, dechlorinate, cycle the filter, plant, and walk you through seasonal care.

Est. 1991 · Lic # 58161-H
Frequently Asked

Answers before
you call.

01

How deep does a koi pond need to be on Long Island?

At least 3 ft. so koi can overwinter below the ice line — we build most at 3.5–4 ft. Shallower ponds work for ecosystem builds with plants and small goldfish, but true koi ponds need real depth on Long Island.

02

How much does a custom koi pond cost?

Most residential koi ponds in Suffolk County run $18k–$45k depending on size, filtration, stone selection, and waterfall scope. Pondless waterfalls start around $9k–$15k. We give a written itemized estimate on-site.

03

What's the difference between a koi pond, an ecosystem pond, and a pondless waterfall?

A koi pond is fish-first — deeper, heavier filtration, minimal plants. An ecosystem pond is plant-first — shallower zones, bog filtration, mixed fish and native plants. A pondless waterfall is a recirculating waterfall over a hidden gravel basin, with no open water and no fish care.

04

Do koi ponds need permits in Suffolk County?

Depth and location can trigger local rules in Brookhaven, Islip, and other towns. We handle any permitting in-house under License # 58161-H.

05

How much maintenance does a koi pond need?

With sized filtration and a UV clarifier, most well-built koi ponds need a spring open, a fall closing, and a full drain-and-clean once a year. We offer maintenance visits on ponds we build and on ponds installed by others in our coverage area.

06

Can I convert an existing pond that leaks or is under-filtered?

Yes — pond renovation is a large share of our water-feature work. We isolate leaks, re-liner where needed, upsize filtration, and re-set the waterfall and stone edge. Most failed pond-kit installs can be saved without a full rebuild.

07

Are pondless waterfalls safer than koi ponds?

Yes — pondless waterfalls have no open standing water; the pump and reservoir sit under a grate. That makes them the default choice for front yards, courtyards, and homes with young children.

08

Will fish survive Long Island winters in a koi pond?

Yes — with correct depth (3 ft.+), a floating de-icer to keep a gas-exchange hole open, and an aerator to keep water oxygenated below the ice, koi overwinter fine here every year.

09

Do you also install lighting and auto-fill?

Yes — underwater LED lighting and an auto-fill valve are standard on every pond, waterfall, and fountain we build. It's the difference between a feature you use at night and one you don't.

10

What Long Island towns do you build ponds in?

Medford, Bellport, Patchogue, Holbrook, Ronkonkoma, Sayville, Blue Point, East Patchogue, Bayport, Farmingville, Selden, Center Moriches, and neighboring communities. Call (631) 480-3238 to confirm coverage for your address.

Financing Available

Build now.
Pay monthly.

Flexible monthly payment plans for patios, driveways, and outdoor living projects across Suffolk County. Licensed & insured. Free estimates.

60-120mo
Terms
Hearth
Lending Partner
Fast
Approval
Outdoor living space with patio built by APM O'Neill & Sons

Financing provided by Hearth. 60-120 month terms. Subject to credit approval. Rates and terms vary by lender.