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How to Care for Pond Fish – The Ultimate Guide

    How to Care for Pond FishFish are the jewel of any pond. Their beautiful colors add sparkle to your backyard oasis, and you, your children and your guests will love watching them dart around the rocks and plants.

    And they’re some of the easiest pets you’ll ever own.

    Pond fish like koi and goldfish ask for little more than food and shelter in return for all the joy they bring. This guide will walk you through everything you need to know about caring for common pond fish, and provide lots of links to articles where you can learn even more.

    Let’s dive in.

    IN THIS GUIDE: How to Care for Pond Fish

    Why Add Fish to Your Pond?

    Healthy Koi FishLet’s talk about why you have those koi, goldfish or other finned friends in the first place.

    Fish aren’t just pretty. You might be surprised by just how much personality a fish can have. Some can learn to take treats out of your hand and might even swim to the pond’s edge when you walk by, waiting for a snack.

    Fish also play a crucial role in your pond’s ecosystem by eating mosquito larvae and other nuisance bugs that otherwise make a home in your pond. What more could you want in a pet?

    How to Build a Pond for Fish

    There are a few schools of thought when it comes to how to build the best pond for koi or goldfish. Some hobbyists prefer what we call “koi museums” – micro-managed environments for very expensive fish. We’re not in that camp. We prefer Ecosystem Ponds.

    An Ecosystem Pond is simply a water feature that uses some clever man-made tricks to replicate processes that happen in nature, creating a super low-maintenance environment where you can enjoy crystal-clear water and happy, healthy fish in a beautiful, natural-looking environment.

    You can read our full guide on Ecosystem Ponds here, but here’s a quick summary of how they work:

    • A skimmer removes 80 to 90 percent of the physical debris that enters your pond.
    • A biofilter has lots of nooks and crannies where beneficial bacteria colonize. These bacteria help keep your water clear. The water runs up through the biofilter then out through your waterfall.
    • Fish-safe EPDM liner keeps water where it’s supposed to be: in your pond.
    • Heavy-duty underlayment protects the liner.
    • Gravel on the bottom of the pond gives beneficial bacteria another place to colonize.
    • A stepped-shelf design gives you a place to add plants, and your family and pets a way to safely enter and exit the pond.
    • Fish caves give your fish a place to get out of the elements and away from predators.

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    What Kinds of Fish Can I Put in My Pond?

    So you’ve decided to add fish to your pond. Now you need to decide what exactly you’re going to put in there.

    The variety of choices might surprise you.

    When people think of pond fish, they most often think of koi and goldfish. Lots of other fish, however, can also make great additions. And even if you decide to stick with classic koi or goldfish, you can still find something unique for your pond.


    Koi Pond FishKoi are the gold standard when it comes to pond fish.

    These majestic swimmers are the descendants of wild Asian carp, selectively bred over centuries to create the eye-catching colors that make them so beloved today. You can buy standard koi, which have short fins, or butterfly koi, which have long, flowing fins.

    Most koi grow to a length of about 12 to 15 inches. Some varieties, though, can reach lengths of up to 3 feet! Their size makes them a poor choice for tiny ponds, but a great addition to ponds where they have a little space – both in terms of depth and pond size – to exercise their swimming muscles.


    ShubunkinEveryone knows what a goldfish is. But did you know they come in lots of colors aside from gold?

    Sarasa goldfish are white with orange spots, for example, while shubunkins are bluish with flecks of black and orange. Goldfish also come in different shapes. Fantails have wide, multi-sectioned tails that fan out behind them like a train on a wedding gown, while other fancy varieties have round bodies or bulging eyes.

    Goldfish usually don’t grow much larger than 8 inches long, making them a good choice for smaller ponds and large containers.


    Catfish can make a neat addition to the right ponds.

    These whiskered fish grow very quickly – sometimes reaching lengths of 2 feet or longer – making them a poor choice for small ponds. If you have the space, though, they can make a good addition to your aquatic ecosystem.

    By the way, don’t buy catfish if you’re looking for something to clean algae out of your pond. While most fish – catfish included – will nibble on algae, they won’t eat enough to make a real difference in the appearance of the pond.

    Golden Orfes

    Golden OrfeGolden Orfes are one of the lesser known pond fish among people new to the hobby.

    These delightful additions look like long, slender goldfish and are usually pale orange or pinkish in color. They grow quickly, often reaching about a foot in length by the end of their first year.

    The trait that makes golden orfes stand out is the way they school with each other. They love to zip around your pond in groups, always sticking close to their buddies.

    High-Fin Sharks

    Hi-Fin Banded Shark

    High-fin sharks – Myxocyprinus asiaticus – are some of the coolest fish you can add to your pond.

    Although not actually related to sharks, these docile algae-eaters have unique triangular dorsal fins that stick out of the water on the rare occasions when they approach the surface.

    Other Fish

    The two biggest factors that will determine whether a fish can live in your pond are size and temperature. First, the fish needs to be able to survive the summer highs and winter lows of your climate – especially if you have a shallow pond more prone to temperature fluctuations. You also need to have enough space to accommodate the fish’s adult size. Contrary to myth, most fish won’t simply stop growing if they’re in a smaller container.

    We’ve created acre-size lakes that house everything from bluegills to daphnia, and tiny ponds that only hold a few goldfish. If you pick the right fish, your options are almost limitless.

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    Basic Pond Fish Care

    Pond fish are incredibly easy to care for if you keep them in a well-built pond. Here are some basics to keep in mind as you welcome your new pets.

    How Many Fish Can I Have in My Pond?

    The rule of thumb for pond fish is to limit your finned population to one inch of fish per every 10 gallons of water in your pond. The actual number of fish your pond can house, though, ultimately depends on the quality of your filtration system. A huge, poorly filtered pond can sustain fewer fish than a tiny pond with excellent filtration.

    What does excellent filtration look like? At its most basic level, a well-filtered Ecosystem Pond should have a skimmer that pulls out physical debris (i.e. leaves) and a biofilter that gives beneficial bacteria a place to colonize. You’ll know your filtration is good if your water is crystal-clear and your fish are happy and healthy.

    How Often Should I Feed My Pond Fish?

    Feeding Koi FishMost people feed their fish about once a day during the warm months. Don’t fret if you miss a feeding or two; your fish will stay happy for a few days or even longer by snacking on the bugs and plants in your pond.

    Only feed your fish as much food as they’ll eat within about five minutes of you throwing it into the pond, and only feed them when the water temperature is above 55 degrees. Switch to a cold water food during the late fall and early spring. (Keep reading for more tips for cold-weather pond care.)

    How Do I Keep My Pond Water Clear?

    What’s the point in having fish if you can’t see them?

    Your pond water should stay clear if you have adequate filtration – a big-enough biofilter and skimmer – and add a weekly dose of beneficial bacteria during the warm months. If your pond water is still murky, you can take some steps to clear it up. Click here to read our tips for keeping water clear.

    Green water, by the way, won’t hurt fish. They can manage just fine as long as the water quality – i.e. ammonia level – is otherwise OK.

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    Seasonal Pond Fish Care

    Fish don’t need much from us in terms of care – just a place to swim, some food to eat and a little attention during seasonal transitions to help them deal with changing temperatures.

    Fall Pond Fish Care

    • Install netting over the pond in early autumn to keep out falling leaves. Remove later in the season, ideally before first snowfall. You can install netting yourself or hire a professional.
    • Switch to cold water fish food when the water temperature is between 55 and 65 degrees to help your fish transition into winter.

    Winter Pond Fish Care

    Swim Pond in Winter

    • Decide whether to keep your pond running or turn it off for the season – also know as winterizing.
    • Install an aerator.
    • Install a deicer.
    • If your pond surface ices over completely, carefully cut or melt a hole.
    • Do not feed fish when the water temperature is below 55 degrees.
    • Do not bring pond fish like koi and goldfish inside for the winter unless they’re being housed in a patio bowl or very small pond. They enter a natural state of near-hibernation in cold temperatures and will survive just fine as long as the pond is deep enough and has adequate aeration.

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    Spring Pond Clean-Out

    Spring Pond Care

    • Turn the pump back on if it was turned off for the winter.
    • Clean out your pond if needed. You can do this yourself or hire a professional.
    • Feed fish a cold water food or probiotic food to help them transition into warmer weather.

    Summer Pond Care

    • Add an aerator to keep water oxygenated.
    • Keep up with regular maintenance.

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    Protecting Fish from Predators

    Koi and goldfish aren’t exactly bred for camouflage.

    Herons, hawks, minks, raccoons and other predators sometimes try to make a snack of pond fish. You can take a few simple steps to prevent that from happening:

    • Include fish caves in your pond design so your finned friends have a place to hide.
    • Install a ScareCrow or similar motion-activated device that spritzes approaching animals with water and deters them from approaching your pond.
    • Add a floating alligator to your pond. The alligator moves with the flow of the water, making it more intimidating than stationary decoys.

    If all else fails, consult a professional for a custom solution. We can build structures that keep away some of the smarter and more determined critters while still letting you look at and enjoy your fish.

    You might notice our list of predator deterrents doesn’t include fishing line or decoy heron. Here’s the truth: They don’t work. Heron have no problem stepping over fishing line, and they quickly learn that a decoy that doesn’t move doesn’t pose much of a threat.

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    Keeping Your Fish Healthy

    Koi Fish Care

    Following the tips above should help you keep your fish happy and healthy. Nature, however, is unpredictable, and fish do sometimes get sick. If that happens, you can take some steps to help them feel better.

    Preventing Fish Loss and Illness

    • Follow all acclimation instructions you receive when you buy new fish.
    • Only add as many fish to your pond as your filtration can handle.
    • Keep debris at a minimum. Excess food, fallen leaves and other gunk all decay in your pond, creating ammonia. Don’t feed your fish more than they’ll eat in a few minutes, and invest in a skimmer to help remove other organic material from the pond.
    • Keep a bottle of Pond Detoxifier on-hand at all times. This product removes ammonia and chloramines from the water. Use it any time you add a significant amount of hose water to your pond, like if you do a water change or accidentally forget to turn off the hose when you top off the pond.
    • Use an aerator to keep water adequately oxygenated, especially in the winter and summer.
    • Only buy fish from reputable suppliers.

    Treating Common Fish Ailments

    Everybody gets sick sometimes – including fish. Pond fish sometimes fall ill with fungal infections, bacterial infections or parasites.

    The first treatment we recommend for almost any fish illness is a combination of non-iodized pond salt and probiotic fish food. Salt builds up your fish’s slime coat and helps its gills work better under stress, while probiotic food boosts the fish’s immune system.

    You can also buy ailment-specific products to treat everything from fungus to ulcers. Just make sure to follow all instructions on the label of anything you add to your pond, and keep in mind that scaleless fish – i.e. catfish – require much lower doses of medication than pondmates like koi and goldfish.

    No matter what treatment you use, we recommend against removing sick fish from your pond in most situations. Fish often heal better when they’re around their friends and tend to decline more quickly when they’re on their own.

    You also have the option of testing your water if something seems off with your fish. While we rarely test the water in our ponds – there’s just no reason to do so if everyone seems healthy – we often test customers’ water for pH, nitrite, nitrate and ammonia levels when they have problems with their fish. If you live near York, PA, you can bring your water to us at Splash, and we’ll test if for free.

    Luckily, pond fish rarely get sick if you take care of them properly. Even a simple goldfish can live to a ripe age of  5 or more, while koi often live into their 20s. If you ever have questions about your fish’s health, don’t hesitate to call us at 717-751-2108.

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