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I started off with 4-inch koi and now they’re 8 inches. How big will they get before they stop growing? | Decorative Ponds & Water Gardens Q & A

Q: I started off with 4-inch koi and now they’re 8 inches. How big will they get before they stop growing?

Q: I started off with 4-inch koi and now they’re 8 inches. How big will they get before they stop growing?

Lauren – Lincoln, NE

A:  In an ideal environment—a supersize space with pristine water conditions at a stable 75 degrees Fahrenheit—an adult koi can reach a whopping 3 feet long. A yard! Nearly a full meter! Yep, that’s a really big fish.

Don’t worry: Chances are slim that your finned pal will grow to that immense length, but you can help it reach its full potential. Koi will keep growing and growing throughout their lives, sometimes faster than others. How fast and large they grow depend on several factors, including:

  • Water quality. Clean water pumped full of oxygen will promote a fish’s health and growth, while poor water quality can stunt its growth. Koi will tolerate a dirty, cloudy environment, but their development and vitality will suffer. Make sure you have an aeration kit in place and are using beneficial bacteria from the DefensePAC® to keep the water crystal clear.
  • Water temperature. A steady 75° F will keep koi in a more active growth state where they’re building muscle and body mass like crazy. Cooler or fluctuating water temperatures trigger a slower growth rate as they slow down their metabolism and activity level. If you live anywhere other than in the tropics, expect to see slower growth in the winter months.
  • Nutrition. Food—and how much of it they eat—matters. Fish food that’s packed with protein and vitamins is formulated to help koi grow and develop. Some also contain ingredients that boost your fish’s vibrant colors.
  • Genetics. Genes play a huge role in how large a koi could grow in the right conditions. Colossal parents often produce colossal offspring, and if those fry live in a spacious pond with clean, aerated water and good food, who knows how big they’ll get!
  • Age. Like most living things, koi develop faster when they’re young and slower as they age. Your 4-inch koi quickly doubled in size because they’re still adolescents; as they get older, their growth rate will slow down.

If you have big plans for your koi, give them an ideal ecosystem and good grub. Your colorful friends may not reach that 3- or 4-foot mark—but you never know!

Pond Talk: What’s the largest koi you’ve ever had—or seen in person?

Energy Efficient Design For 24-7 Use - The Pond Guy® Water Garden Aeration Kit

How do I calculate what size basin I need for a pondless waterfall? | Decorative Ponds & Water Gardens Q & A

Q: How do I calculate what size basin I need for a pondless waterfall?

Q: How do I calculate what size basin I need for a pondless waterfall?

Robert – Waverly, TN

A:  With the help of a few friends, installing a pondless waterfall is an easy way to upgrade your land- or waterscape. If you are planning to design and build your own feature, here’s how to do the math to determine your basin size.


Step 1: Calculate total amount of water in your stream

Sound tricky? It’s not. To calculate the water that’s in motion in your stream, first measure your stream’s length, width and depth. Then plug those numbers into this equation: L x W x (0.25 x D of stream, generally 1 to 2 inches) x 7.48.

Here’s an example. If your stream is 25 feet long, 2 feet wide and 1 inch deep, the equation would look like this: 25 x 2 x (0.25 x 1) x 7.48 = 93.5 gallons.

Step 2: Calculate amount of water your basin needs to hold

As a general rule, you will need your basin to hold 2½ times the amount of water in your stream. To find out how much water your basin will need to hold, multiply the gallons of water in your stream by 2.5. In the above example, it would be 93.5 x 2.5 = 233.75 – so your basin would need to hold 233.75 gallons of water.

Step 3: Determine the size basin needed to hold the water

Here’s where things get a little tricky. You’ll likely use boulders, stones and other décor in your design. Well all that rockwork will take up space for water, and so you’ll need to go with a larger vessel.

Try this quick equation that will help you determine what size basin you’ll need with boulders: L x W x D x 2.2 = gallons of water the basin will need to hold. To give you an idea, a 5 foot by 10 foot basin that’s 3 feet deep and contains stone will hold 330 gallons of water.

A space- and cost-saving option is to use a basin matrix in place of some of the boulders. A basin matrix is a strong, 27-by-16-by-17½-inch hollow box that’s perforated with half-inch holes to allow water to collect and pass through. You can stack them together and landscape right over them. Each basin matrix holds 31.5 gallons, adding valuable water volume without increasing the size of the basin. Don’t forget to add a pump vault for easy access to your pump.

Go with a Kit

If you aren’t trying to customize a large waterfall, consider investing in a pond free waterfall kit, like PondBuilder™ Cascading Falls Pondless Kits. They contain all components you’ll need – from underlayment and liner to a waterfall box, pump, basin matrix and plumbing – with predetermined dimensions to help you create your water feature.

Pond Talk: What’s the largest size boulder you’ve installed in your water- or landscape?

Create A Low Maintenance Waterfall - PondBuilder™ Cascading Falls Pondless Kits

What can I do to help out a fish that was attacked by a heron? | Decorative Ponds & Water Gardens Q & A

Q: What can I do to help out a fish that was attacked by a heron?

Q: What can I do to help out a fish that was attacked by a heron?

Lori – Glen Forney, PA

A:  Ouch. A heron attack isn’t pretty – and it’s potentially deadly to your fish. Unfortunately, you can’t call 9-1-1 or an emergency fish veterinarian for a pond call, but you can try some things that could save your pet’s life.


  1. Examine, Triage: The first thing to do is examine the victim and do some triage. Capture the injured fish in a pond net and take a closer look at its wounds without removing it from the water. How severe is the injury? Are there just a few scrapes, or does the fish have an open wound?
  2. Minimal Injuries: If your fish’s injuries aren’t too severe and it appears to be normal except for a few scrapes, leave it in the pond and add some Stress Reducer PLUS to the water. The liquid formula will help to calm the fish and rebuild its slime coat, which defends it against infection. You might also want to add some soothing salt to the water (read about it here).
  3. Remove and Isolate: If your fish is severely injured, set up a quarantine tank with pond water and an aerator, add some Stress Reducer PLUS, put it in a shaded and protected area, and gently move the fish from the pond to the tank.
  4. Watch for Infection: Keep an eye on your fish while it’s in the quarantine tank. Because damaged tissue becomes a breeding ground for bacterial and fungal pathogens, watch for signs of infection. If you see split or ragged fins, slimy patches or red ulcers on its body, or any other unusual symptoms, use CrystalClear® Wipeout™ or API® MelaFix to heal the wounds and restore damaged tissue.

While your finned friend is recovering, makes some plans for how you’ll guard your pond against future attacks. A Blue Heron Decoy will dissuade the real things from stopping by for a snack. Pond netting will prevent birds from reaching the water. Floating, submerged and marginal aquatic plants give your fish somewhere to hide, as do fish shelters, like the Koi Kastle. Set your fish up for safety – especially since that heron will be back for seconds!

Pond Talk: Have you ever nursed a sick fish back to health?

Reduce Stress & Heal Damages Tissue - Pond Logic® Stress Reducer PLUS

What is the difference between a waterfall filter and a waterfall spillway? | Decorative Ponds & Water Gardens Q & A

Q: What is the difference between a waterfall filter and a waterfall spillway?

Q: What is the difference between a waterfall filter and a waterfall spillway?

Ashley – Forest Grove, OR

A:  Waterfall filters and waterfall spillways both generate a flowing waterfall in your pond or water feature – but they have different designs and purposes. Here’s what you need to know about including them in your waterscape.


A Waterfall Filter

A waterfall filter, like The Pond Guy® ClearSpring™ Pro Waterfall Filters, serves two purposes: it generates a waterfall, and it houses your biological filtration system. The waterfall filter provides a starting point for the waterfall itself as the water fills its deep basin and pours evenly over the spillway. That basin is also spacious enough to hold filter media, which houses countless beneficial bacteria – a.k.a. your biological filtration system.

These two-in-one units work well for hobbyists who are building a new pond or are in need of additional filtration. Once you install one, be sure to seed the filter media with PL Gel, a bacterial inoculant that contains beneficial microorganisms and naturally occurring biopolymers that reduce filter startup time.

A Waterfall Spillway

A waterfall spillway, like the PondBuilder™ Elite Cascade Spillways, also provides a starting point for an evenly pouring waterfall, but the basin itself is smaller and provides no room for filter media.

But because it creates the environment-enhancing movement and sound of flowing water, a waterfall spillway makes an excellent addition to a pond that’s already filtered. It also works well for pondless waterfalls and in ponds in areas with little room to work.

Customizing Your Flow

Whether you install a waterfall filter or waterfall spillway, they can both be used in conjunction with a skimmer. You can also easily blend them into your landscape with rock covers or aquatic plants while still allowing you to access the unit. Some models even offer a planting shelf or basket to house additional aquatic plants. Check out our entire selection of Waterfall Filters & Waterfall Spillways.

Pond Talk: What type of waterfall does your pond or water feature have?

Create a Waterfall & Filter Your Pond - The Pond Guy® ClearSpring™ Mini Waterfall Filter

The pH level in my pond always reads high. What can I do to reduce it? | Decorative Ponds & Water Gardens Q & A

Q: The pH level in my pond always reads high. What can I do to reduce it?

Q: The pH level in my pond always reads high. What can I do to reduce it?

Mike – Forest Hills, NY

A:  Your pond’s pH – or potential hydrogen – level is an important measurement to understand because it affects the health of those things swimming around in the water. If your pH level is too high or too low, it could affect your fishes’ ability to reproduce, fight disease and metabolize food. It can also impact the well-being of other living things in your pond, like plants, amphibians and other aquatic critters.

A pH test, like the one found in the API® Pond Master Test Kit, can reveal a lot about your pond. But what does a high or low pH reading mean, and how can you adjust its level – or should you just leave it alone? Read on to learn more about understanding your pH level and how to change it.

Potential Hydrogen Defined

In super simple terms, pH is a measure of how acidic or alkaline a water body is on a scale from 0 to 14. Pure water is neutral. It has a pH close to 7.0 at 77 degrees F. Blood is also close to neutral. Ammonia’s pH is ~11, which is high on the alkaline charts, while stomach acid’s pH is ~1, which acidic enough to burn through your chewed-up chow.

Adjusting to a Proper pH

You don’t have to keep your pond at a perfect 7.0 pH all the time. In fact, an acceptable pH reading for a pond is 6.5 – 8.5, so if your score falls in this range you need not make any changes at all. If it’s outside those levels, however, you will need to make some adjustments. Here are some ways to reduce your pH:

  1. Partial Water Change: Replacing some of your pond water with fresh water is one way to reduce your pH. Remember to treat with water with a conditioner, like Pond Logic® Stress Reducer PLUS, to remove impurities and heavy metals that could be harmful to your fish.
  2. Use pH Reducer: If you need to adjust your pH using a pH stabilizer like pH Lift or pH Drop, apply enough treatment to shift the levels 0.5 at a time, wait several hours before re-treating, and test the waters often with your API® Pond Master Test Kit.
  3. Test Your Water: Try testing your tap water, especially if you’re on a well. If the pH is high from your well, then your pond will stay at about that level and you won’t be able to do much to treat it.
  4. Try Clarity Defense®: A water clarifier like Clarity Defense® can help to add trace minerals while buffering pH to promote stable levels and prevent swings. Plus, it clears cloudy water by locking up excess nutrients and allowing your filter to remove them.

Try these tricks to reduce the pH levels in your pond – but remember to do so very gradually. Good luck!

Pond Talk: How often do you test the pH levels in your pond?

Prevent pH Swings & Keep Fish Safe - Pond Logic® Clarity Defense®

In the DefensePAC, there are three products that are all natural bacteria. Are all three really necessary? | Decorative Ponds & Water Gardens Q & A

Q: In the DefensePAC, there are three products that are all natural bacteria. Are all three really necessary?

Q: In the DefensePAC, there are three products that are all natural bacteria. Are all three really necessary?

Julie – Sandwood, SC

A: Bacteria is bacteria, right? Well, no, not really. In nature, thousands of bacteria species perform many important jobs. The specific strains used in the DefensePAC® were chosen for their unique ability to break down suspended debris and sunken muck in pond water. And they’re really good at what they do.

The three different aerobic natural bacteria products found in DefensePAC® play different roles in your pond. Here’s a bit more about what they are and how they work to keep your water crystal clear.

Nature’s Defense®

The bacteria in Nature’s Defense® are designed to attack organic debris that’s suspended in the water column, like fish waste, uneaten food and leaves. To use, you simply toss the water-soluble packets in the water. The bacteria will immediately go to work breaking down the excess nutrients like phosphates and nitrogen, and multiply every 20 to 40 minutes. We recommend using Nature’s Defense® in conjunction with Muck Defense® in the summer. The result: crystal clear water.

Muck Defense®

To attack the accumulated organic debris that builds up at the bottom of your pond, Muck Defense® comes in bacteria-packed tablets that sink straight down. Upon application, the tablets release bacteria that instantly begin to break down and digest hard-to-reach muck and sludge from the bottom of gravel and rock pond bottoms. We recommend using Muck Defense® in conjunction with Nature’s Defense® in the summer. The result: reduced muck and no pond odor.

Seasonal Defense®

The bacteria in Seasonal Defense® prefer cooler water temperatures, like those in the spring and fall. While Nature’s Defense® and Muck Defense® can be used when the water is above 50 degrees F, Seasonal Defense® is designed to be used when the water is below 50 degrees F. It accelerates the decomposition of leaves, scum and sediment that create pond muck during the fall and winter months, and jump starts the bacteria population in your pond the in spring.

Though Nature’s Defense®, Muck Defense® and Seasonal Defense® all contain beneficial bacteria, they’re designed to do different things in your pond. Are all three necessary? Yes indeed! When used together, you’ll enjoy clear water, a clean pond and reduced muck and odor all year long.

Pond Talk: How long do you spend cleaning your pond from organic debris?

Improve Your Pond's Water Quality - Pond Logic® DefensePAC®

Is there any danger to my fish if the pond is always in direct sunlight? | Decorative Ponds & Water Gardens Q & A

Q: Is there any danger to my fish if the pond is always in direct sunlight?

Q: Is there any danger to my fish if the pond is always in direct sunlight?

Claudia – De Witt, AR

A: Sunshine has its benefits – but it also has its dangers. Direct sunlight with no shade can raise the water temperature in your pond and reduce the levels of oxygen available to your fish. All those rays can also fuel algae blooms, as well as give your fish a sunburn (yes, really!).

Don’t worry: You don’t need to relocate your water feature to a less sunny locale. There are some easy ways to add shade to your pond, and here’s what we recommend.

  • Terrestrial Shade: Trees, and terrestrial and marginal plants growing alongside your pond can provide plenty of shade from the outside. Blue Flag Iris and Dwarf Cattail, for instance, planted on the south or west side will cast cool, shady shadows for your fish.
  • Get Creative with Canopies: If planting trees or plants isn’t an option, consider installing a tent or canopy over part of your pond. In addition to creating protection from the sunshine, a canopy can also add some dramatic flair to your backyard décor.
  • Aquatic Plants: Aquatic plants, like water lilies and water hyacinth, create scads of underwater shade for your finned pals. Simply plant lilies in baskets or plant bags and place them in strategic spots around your pond or toss in water hyacinth to create a floating hideout.
  • Fish Shelters: For a super easy solution, drop some fish shelters, like our Nycon Koi Kastle Fish Shelter, in your water garden. Another option is to create fish caves with carefully positioned rocks. They’ll create a shady shelter that’ll protect the fish from sun – and predators.

A word of advice: Don’t over shade your pond. You still want to maintain an area with some sunlight, which helps bring out koi colors, keep the water a comfortable temperature and help your plants grow.

If you think your fish are already showing signs of heat stress, check your water temperature with a pond thermometer, like Pond Logic® Floating Pond Thermometer, and do a partial water change if the water temperatures reach the high 70s or above. You might also want to add some pond salt, which will help gill function and reduce fish stress, as well as some Stress Reducer PLUS, which alleviates stress, restores a healthy slime coat and removes dangerous toxins from the water.

Pond Talk: Have your koi or pond fish ever had a sunburn?

Give Your Fish a Break from the Sun - Nycon Koi Kastle Fish Shelters


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