How to Build a Koi Pond with a Waterfall in Cincinnati (2025 DIY + Pro Guide)
April 11, 2025
Before You Dig, Planning Your Cincinnati Koi Pond Project
Reading Time : 13-16 Minutes
Permits, Zoning, and Utility Check (Call 811 in Ohio)
Before anything else, call 811. This free service will send technicians to mark underground utility lines like gas, electric, and water — preventing costly or dangerous mistakes during excavation.
In most Cincinnati-area municipalities, koi ponds deeper than 18–24 inches may be considered regulated water features, especially if they require electrical connections (for pumps or lights). Always:
- Check with your city zoning department — particularly in Indian Hill, Blue Ash, and Mason where zoning codes are stricter in residential neighborhoods.
- Ask about property line setbacks — you may need to place your pond several feet away from fences or easements.
- Confirm if child safety fencing is required (usually if the pond exceeds 2 feet deep).
Tip: Serene Aqua can help guide you through the permit process if you prefer to hire a pro.
Choosing the Right Location: Sunlight, Drainage, and Safety
Location is everything — and your koi fish will thank you later.
How Much Sunlight?
Ideally, a koi pond should receive 4–6 hours of sunlight per day. Full sun all day can lead to:
- Algae blooms
- Elevated water temperatures
- Poor oxygenation
Conversely, too much shade (like under large trees) leads to:
- Falling leaves and debris
- Cooler water and slower plant growth
Aim for a partial-shade spot, or consider using shade plants and shade sails for balance.
Ground Drainage Matters
Cincinnati’s soil is often clay-based — which means poor drainage. Avoid placing your pond:
- At the bottom of a slope where runoff could flood the pond
- Near downspouts or gutters
If necessary, grade the area and install a French drain or perimeter gravel trench to redirect surface water.
Safety Around Kids and Pets
For family homes, choose a visible spot that’s away from play areas and walkways. Consider installing:
- Low fencing or landscaping borders
- Motion sensor lights for nighttime visibility
- Gradual pond edges or shelves instead of steep drop-offs
Designing for Function & Beauty: Natural vs. Modern Pond Styles
Now for the fun part — picking your pond’s personality.
There are three primary koi pond styles you’ll see in Cincinnati backyards:
1. Natural Ponds
- Organic shapes (no perfect circles)
- Surrounded by boulders, native plants, and mulch
- Often include a gravel bottom and waterfall feature
- Designed to blend with the landscape
These are ideal for homeowners in rural or wooded areas like Indian Hill or Anderson Township.
2. Formal Ponds
- Geometric shapes (squares, rectangles)
- Often set in concrete or stone
- Minimal plant life, focusing on clear visibility of koi
- May include fountains instead of waterfalls
Popular in modern homes or small yards in neighborhoods like Hyde Park or Blue Ash.
3. Hybrid/Modern Ponds
- Clean design but with natural elements
- May include UV filtration, LED lighting, or smart aeration systems
- Great for homeowners who want low-maintenance and aesthetics combined
Design Tip: Use local stone or flagstone from Ohio quarries to enhance your pond’s natural look and support regional material sourcing.
How Deep Should a Koi Pond Be in Cincinnati Winters?
This is one of the most important questions for local homeowners — and it’s often misunderstood.
In southern Ohio, winters are cold enough to freeze pond surfaces, but not usually so severe that ponds freeze solid — if they’re deep enough.
- Minimum Depth: 2 feet (absolute minimum)
- Recommended Depth: 3 to 4 feet
- Ideal for Fish Health: 4–5 feet (for year-round koi care)
Shallow ponds risk:
- Fish mortality from temperature shock
- Water quality issues due to reduced oxygen levels
- Complete freezing in extremely cold years (e.g., 2014 and 2021)
Want to avoid fish loss? Add a pond de-icer and aerator to maintain oxygen during freeze cycles. Serene Aqua installs these systems with all four-season pond builds
Materials & Tools Checklist for a Koi Pond Build
You don’t need a warehouse of tools to build a koi pond — but having the right equipment upfront saves major headaches. Below is a checklist used by both DIYers and pros like the Serene Aqua team.
Must-Have Equipment for DIY Builders
Tool | Purpose |
Shovel + Spade | For digging pond and shaping shelves |
Wheelbarrow | To move soil, gravel, and rock |
Rake | Smooth underlayment and gravel |
Garden Hose | For filling, rinsing, and layout guides |
Tape Measure | Essential for planning depth and volume |
Level | Ensures skimmer, waterfall, and liner are even |
Utility Knife | Cuts liner to shape (don’t forget extra blades!) |
Pond Liners, Skimmers, Pumps, and Biofalls Explained
Let’s quickly demystify the gear behind a healthy koi pond.
Pond Liner (EPDM or Rubber)
- Flexible, durable, UV-resistant
- EPDM liners can last 20–30 years
- Ensure underlayment beneath to prevent root punctures
Skimmer Box
- Skims leaves, debris, and surface scum
- Reduces clogging of pumps and filters
- Should be placed where wind naturally blows debris
Water Pump
- Must circulate entire pond volume every hour
- For example, a 1,500-gallon pond needs a 1,500 GPH pump
- Choose energy-efficient submersible pumps for most DIY builds
Biofalls/Waterfall Box
- Provides both aeration and filtration
- Houses beneficial bacteria to break down waste
- Doubles as a decorative waterfall outlet
Serene Aqua’s pro tip: Always oversize your pump and filtration slightly. This gives flexibility if you expand or add fish later.
Step-by-Step: How to Build a Koi Pond
with a Waterfall in 9 Steps
You’ve finalized your design, marked your layout, and gathered the right materials. Now it’s time to bring your backyard oasis to life. This step-by-step process is based on real-world best practices, adapted specifically for Ohio’s climate and soil conditions. Whether you’re building a small decorative pond or a full-featured koi habitat, following these nine steps will ensure long-term success.
Step 1: Mark Your Pond Layout and Depth Zones
Use spray paint, string, or a garden hose to outline the shape of your pond. If you plan to build plant shelves, rocks, or a waterfall, mark these areas as well. Multiple depth zones offer several advantages:
- Shallow shelves for aquatic plants
- Mid-levels for swimming zones
- Deep pockets (at least 3 to 4 feet) for overwintering koi
Double-check dimensions before digging. Mistakes in layout can affect pump size, liner fit, and flow rates for waterfalls.
Step 2: Excavating with Shelves for Plants and Fish Safety
Begin digging based on the marked outline, creating gentle slopes instead of vertical walls. A tiered excavation approach is recommended:
- Dig the perimeter 12 to 18 inches deep.
- Move inward and dig the middle zone another 12 to 18 inches.
- Create the deepest section at the center, ensuring at least 3 feet for wintering koi.
Include shallow ledges for marginal plants and lights. This makes maintenance easier and prevents liner damage during planting.
Cincinnati’s heavy clay soil can retain water after rain, so be cautious about working after storms to avoid soil collapse or waterlogging.
Step 3: Installing Liner, Underlayment, and Edge Protection
Line the excavated pond with a protective underlayment made of geotextile fabric or old carpet padding. This layer prevents punctures from rocks, roots, and shifting soil.
Next, lay out your flexible pond liner (EPDM rubber is preferred for durability). Spread the liner loosely so it can conform to the shape without pulling or stretching. Use large flat rocks around the perimeter to secure it temporarily.
Key tips:
- Allow 12–18 inches of liner overhang beyond the pond edge.
- Avoid sharp folds; smooth the liner gradually from the center outward.
- Create protective edge zones with rock coping to prevent runoff contamination and UV degradation.
Step 4: Setting Up Filtration, Water Pump, and Skimmer Box
A healthy koi pond starts with proper filtration. For Cincinnati homeowners, this is even more important due to seasonal changes and organic debris from native trees.
Install the skimmer box at the edge of the pond where wind tends to push surface debris. Cut a hole in the liner where the skimmer will go, and seal the faceplate with pond-safe silicone to prevent leaks.
Place the water pump inside the skimmer box or in a separate pump vault if you’re using a bottom-drain system. Connect the pump to the biofalls (waterfall box) using flexible kink-free tubing.
Sizing tips:
- Your pump should circulate the full pond volume every hour.
- Choose a pump that matches the height (head pressure) and length of tubing to your waterfall box.
If your waterfall is elevated by 2 feet and the tubing is 20 feet long, select a pump that handles both flow rate and lift efficiently.
Step 5: Building the Waterfall and Biofalls
Position the biofalls box at a higher elevation than the pond to allow gravity to feed the waterfall. Build a sturdy base using compacted soil, bricks, or concrete blocks. Place the box level and secure it in place.
Surround the box with large fieldstone, flagstone, or boulders to create a natural cascade. Use waterfall foam between the rocks to control the water’s direction and minimize leakage behind the stones.
Key details for a successful waterfall:
- Keep the flow smooth and natural-looking.
- Layer larger stones around the spillway and taper into smaller stones toward the base.
- Hide tubing and connections with additional rocks or plants.
The biofalls also houses beneficial bacteria that clean your pond water as it flows back in — essential for keeping koi healthy.
Step 6: Adding Rocks, Gravel, and Decorative Borders
Begin lining the pond bottom with smooth river rock or rounded gravel, at least 2 to 3 inches deep. Avoid sharp-edged stones that can tear the liner or injure fish.
Add larger decorative boulders along the sides and shelves to enhance the natural look and secure the liner in place.
Why rocks and gravel matter:
- Offer surface area for beneficial bacteria (bio-filtration)
- Help weigh down the liner
- Prevent UV damage and algae buildup
- Provide hiding spots for fish
Around the perimeter, use pavers or stone coping to create a defined edge that blends with your landscape. Avoid mulch or loose soil near the edge to reduce contamination risks.
Step 7: Installing Lights, Aerators, and Optional Add-Ons
Once the core pond and waterfall structure is in place, you can enhance its function and beauty with add-ons. Consider installing:
- Underwater LED lights for nighttime ambiance
- Aeration systems to improve oxygen levels, especially in summer
- Auto-fill valves connected to a hose bib to maintain water levels
- De-icers to keep a hole open in winter, allowing gas exchange
In colder regions like Cincinnati, pond heaters and floating aerators can be life-saving for koi during freeze cycles.
These upgrades aren’t essential for the build, but they greatly improve the pond’s resilience and make it more enjoyable throughout the year.
Step 8: Filling, Testing for Leaks, and Adjusting Water Chemistry
Begin filling the pond slowly with a garden hose. As the water rises, continue smoothing out the liner and adjusting rocks or edges as needed.
Watch for signs of leaks:
- Dropping water level during fill
- Wet areas around the liner or plumbing
- Flowing water behind the waterfall rocks
If all looks good, allow the pond to fill fully and then test water quality using a pond test kit. Tap water in Cincinnati may contain chlorine or chloramine, so use a water conditioner before introducing fish.
Recommended parameters:
- pH: 7.0 to 8.0
- Ammonia: 0 ppm
- Nitrites: 0 ppm
- Temperature: 65–75°F (in spring/summer)
You may need to run your pump and filter for a few days before the water stabilizes.
Step 9: Adding Aquatic Plants and Introducing Koi Fish
Once your pond water is clear and tests are within range, begin adding life to your ecosystem.
Start with aquatic plants:
- Floating plants: water lettuce, water hyacinth
- Marginal plants: cattails, iris, arrowhead
- Oxygenators: hornwort, anacharis
Plants will oxygenate the water, reduce algae growth, and provide shelter for koi.
When adding fish:
- Acclimate koi by floating their bag in the pond for 15 to 30 minutes.
- Gradually mix pond water into the bag before releasing them.
- Start with a small number (3 to 5 fish) and observe for stress or illness.
Do not overstock. Koi need space to swim and grow. Begin with fewer fish and let your pond’s ecosystem mature before expanding.
Long-Term Care for Your Backyard Pond
After completing your koi pond build, ongoing maintenance becomes essential. A well-maintained pond will reward you with clear water, healthy fish, and a landscape feature that looks great year-round. Cincinnati’s climate presents unique seasonal challenges, so this section covers weekly, monthly, and seasonal care tips along with solutions for common pond problems.
Weekly Maintenance Tasks for Clean, Clear Water
Most koi pond upkeep involves small, consistent tasks. Ignoring routine maintenance can lead to algae buildup, foul odors, and unhealthy water conditions.
Skimmer Cleaning
Remove leaves and debris from the skimmer basket once or twice per week, especially during fall. This helps reduce ammonia buildup and prevents clogging the pump.
Filter Inspections
Check your mechanical and biological filtration components. Rinse sponge filters with pond water (never tap water) to preserve beneficial bacteria.
Surface Debris Removal
Use a long-handled net to remove floating leaves or plant debris before they sink. This minimizes nutrient overload, which feeds algae.
Water Top-Off and Conditioning
Hot summer days often cause evaporation. Top off the pond with a garden hose and add a water conditioner if using tap water to neutralize chlorine and chloramine.
Seasonal Pond Care in Ohio’s Climate
Southern Ohio’s weather includes freezing winters, rainy springs, and humid summers. Each season brings different care priorities for your pond.
Spring Pond Startup
Once temperatures rise consistently above 50°F:
- Remove any remaining pond covers or de-icers
- Clean out sludge or organic buildup using a pond vacuum
- Reconnect filters, pumps, and aerators
- Begin feeding koi again with cold-weather food (high wheat germ content)
This is also the best time to divide aquatic plants and check for liner or plumbing damage.
Summer Pond Management
As temperatures peak in July and August:
- Monitor oxygen levels — warm water holds less oxygen
- Consider adding floating plants to provide shade
- Test water weekly for ammonia and nitrite levels
- Increase aeration using additional diffusers or waterfalls
Pond fans or shade sails can help reduce temperature spikes in shallow ponds.
Fall Preparation
In late September through November:
- Net your pond to catch falling leaves
- Slowly reduce fish feeding as water cools
- Trim back hardy aquatic plants
- Remove tropical plants or bring them indoors
- Shut down UV clarifiers if temperatures drop below 50°F
Fall is also a great time for a partial water change to refresh the ecosystem before winter.
Winterization in Cincinnati
For ponds deeper than 3 feet, koi can overwinter in place — but you must maintain proper gas exchange.
- Install a pond de-icer to keep a small area ice-free
- Run a low-wattage aerator near the surface (not at the bottom)
- Do not break ice by force — this shocks and stresses fish
- Stop feeding once water temperatures stay below 45°F
Shallow ponds or those under 2.5 feet deep may require temporary indoor housing for koi during January and February cold spells.
Troubleshooting Cloudy Water, Algae, and Sick Fish
Even with excellent planning and equipment, koi ponds are living ecosystems — and problems may still arise. Knowing what to watch for helps you act quickly.
Green or Murky Water
Likely causes:
- Excess sunlight
- Poor filtration
- Overfeeding or high organic matter
Solutions:
- Add more shade via floating plants
- Upgrade biological filtration or install a UV clarifier
- Cut back on feeding or remove rotting debris
If the water turns brown or tea-colored, it could be tannins from leaves. Activated carbon in a mesh bag may help clear it.
String Algae or Algae Blooms
String algae clings to rocks and waterfalls. Blooms make the water green and murky. While algae is natural, too much indicates imbalance.
Best practices:
- Maintain a strong population of aquatic plants
- Avoid chemical algaecides, which can harm fish
- Use barley straw or natural enzyme treatments as a preventative
Some Cincinnati homeowners add small fish like grass carp or algae-eating snails, though these must be introduced carefully.
Sick or Lethargic Fish
Watch for symptoms:
- Gasping at the surface
- Sores or ulcers
- Unusual swimming behavior
- Staying still at the bottom of the pond
Actions to take:
- Test water quality immediately (pH, ammonia, nitrites)
- Isolate affected fish in a separate holding tank
- Consult a pond specialist or vet if symptoms persist
Most koi illnesses stem from poor water quality, overcrowding, or abrupt temperature changes. Prevention is the best approach.
Ready to Build a Peaceful Backyard Retreat?
By now, you have a full understanding of how to build a koi pond with a waterfall — from planning and excavation to long-term care. But even the best guides can’t replace hands-on experience. Whether you’re still weighing a DIY approach or ready to hire a professional, this final section offers a recap, preparation checklist, and insights into how Serene Aqua can help Cincinnati homeowners bring their backyard visions to life.
Summary: What Makes a Successful Koi Pond Build?
A koi pond isn’t just a hole in the ground with water. It’s a living, breathing ecosystem that requires proper planning, materials, filtration, and care.
Here’s what every Cincinnati pond should include:
- A minimum depth of 3 to 4 feet for fish safety and winter survival
- A balanced mix of shade and sun, ideally 4–6 hours of daily sunlight
- Quality filtration, including a mechanical skimmer and biological biofalls
- Rocks and gravel to support bacteria and create a natural appearance
- Seasonal adaptations like aeration and de-icers for Ohio winters
- A thoughtful design that complements your home and landscape
If you include lighting, automation, and native planting, your pond becomes more than a weekend project — it becomes a daily escape.
Ready to Build a Peaceful Backyard Retreat?
By now, you have a full understanding of how to build a koi pond with a waterfall — from planning and excavation to long-term care. But even the best guides can’t replace hands-on experience. Whether you’re still weighing a DIY approach or ready to hire a professional, this final section offers a recap, preparation checklist, and insights into how Serene Aqua can help Cincinnati homeowners bring their backyard visions to life.
Summary: What Makes a Successful Koi Pond Build?
A koi pond isn’t just a hole in the ground with water. It’s a living, breathing ecosystem that requires proper planning, materials, filtration, and care.
Here’s what every Cincinnati pond should include:
- A minimum depth of 3 to 4 feet for fish safety and winter survival
- A balanced mix of shade and sun, ideally 4–6 hours of daily sunlight
- Quality filtration, including a mechanical skimmer and biological biofalls
- Rocks and gravel to support bacteria and create a natural appearance
- Seasonal adaptations like aeration and de-icers for Ohio winters
- A thoughtful design that complements your home and landscape
If you include lighting, automation, and native planting, your pond becomes more than a weekend project — it becomes a daily escape.
Why Homeowners Across Cincinnati Choose Serene Aqua
Serene Aqua has built and maintained koi ponds and hardscape water features throughout the Greater Cincinnati area. Our team understands the regional weather, soil, and landscaping trends that impact pond design.
We handle every part of the process:
- Custom koi pond and waterfall design
- Full excavation, grading, and drainage planning
- Skimmer and filter system installation
- Flagstone and rock placement for structural beauty
- Integration with existing patios, decks, and gardens
- Seasonal startup, shutdown, and year-round maintenance
Every project is built to last — and designed to impress.
Areas We Serve
We provide koi pond installation, design, and repair services in:
- Cincinnati
- Mason
- Indian Hill
- Blue Ash
- Hyde Park
- Loveland
- Madeira
- Anderson Township
- West Chester
- Northern Kentucky (upon request)
If you’re in or around these neighborhoods, we offer in-person consultations and free site evaluations.
Get a Free Quote from Serene Aqua
Whether you’re just beginning to sketch ideas or ready to move forward with construction, Serene Aqua offers expert guidance and high-quality craftsmanship. Our ponds are designed for Cincinnati’s weather, built to last, and backed by professional support.
Call us today or request a quote online to speak with a pond installation specialist. We’ll help you explore design options, compare DIY vs. professional costs, and guide you through every step.
Key Takeaways: Building a Koi Pond in Cincinnati
- Local Considerations Matter
Cincinnati’s winters, clay-heavy soil, and variable elevation all affect how you build a pond that lasts. - Depth and Filtration Are Essential
For koi survival and water clarity, your pond needs to be at least 3 feet deep and include both mechanical and biological filtration. - Maintenance Starts on Day One
From water testing to debris removal, proactive care leads to a healthy pond ecosystem. - DIY vs. Pro Is About Time, Tools, and Experience
Homeowners with landscape experience may enjoy the DIY process, but many prefer the peace of mind of hiring a licensed, full-service installer. - Serene Aqua Builds Peace of Mind
Our team combines hardscape design, pond installation, and eco-conscious planning to deliver water features that function beautifully — year after year.
Frequently Asked Questions: Koi Ponds in Cincinnati
Sources Used
- Ohio Utility Protection Service. “Call 811 Before You Dig.” 2024.
- Cincinnati Zoning Code. “Residential Landscape & Water Feature Requirements.” City of Cincinnati, 2023.
- Ohio State University Extension. “Backyard Ponds and Water Features.” OSU Extension, 2022.
- National Weather Service. “Cincinnati Average Winter Temperature Summary.” NOAA, 2023.
- The Pond Guy. “Pond Building Checklist and Water Garden Design Tips.” 2024.
- Aquascape Inc. “Best Practices for Ecosystem Ponds.” 2023.