7 Biggest Koi Pond Mistakes

Nick Durante
by Nick Durante
Credit: Shutterstock / kwangmoozaa

Koi ponds are beautiful and lively, and they can make your yard more enjoyable. That said, it’s quite easy to make mistakes that can harm the fish in your pond. Many of the biggest koi pond mistakes are easy to overlook.

The biggest koi pond mistakes include overpopulating the pond and putting too many plants in the water. It’s also a big mistake to feed the koi food with too many carbohydrates, as it will negatively affect their digestion. Try to use sand and chunky gravel as a substrate to encourage healthy bacteria growth and reduce choking hazards.

Never overpopulate your pond with small koi, as they can grow to be 15” and take up a lot of space. Follow along as we highlight the 7 biggest koi pond mistakes to avoid.

7 Avoidable Koi Pond Mistakes

1. Too Many Plants

As tempting as it may be, you can overcrowd your koi pond if you put too many plants in it. Ideally, you should leave at least 40% to 50% of the surface and substrate free of plants. The pond will be hard for the koi to navigate if over 60% of the pond features plants.

That said, it’s important to find a balance, as koi love plants, and it helps their ecosystem. Plants provide hiding spots and shade that improve the quality of life for the koi in the pond. The presence of plants can help oxygenate the fish as well, and that’s necessary.

Avoid plants like water hibiscus, as they are invasive in many areas. Invasive plants can take over koi ponds, and they are more trouble than they are worth.

2. Failure To Monitor Fish

It’s all too easy to get wrapped up in the nuances of koi ponds and forget to monitor the fish themselves. Watch your koi closely to check for signs of disease and behavioral changes. You can often tell that something is wrong with your koi if they suddenly lack energy.

Another sign that they are unhealthy is that they either stay at the bottom or the top of the pond. Low oxygen levels are possible if the fish stick toward the top of the pond. If they stay at the bottom of the pond, it could be a sign that they are sick, overcrowded, or anxious.

Keep in mind that there is a lot of trial and error when it comes to koi ponds. Because of that, you must pay attention to any changes within the pond that trigger behavioral changes. Watch their swimming patterns, breathing habits, diet, and gills to monitor their health.

3. Choosing The Wrong Food

Today, so many brands sell food meant specifically for koi ponds, but it’s not always great. For example, fish food that is high in carbohydrates can be quite bad for koi. They can’t easily digest carbohydrates, and they will likely become lethargic.

The ideal food for your pond also depends on the size and type of koi fish you have. For example, big, adult koi fish typically need food bars that contain shrimp and are high in protein. Small koi fish can thrive off of pebble food, as long as it is rich with nutrients.

4. Overcrowding

While it’s exciting to have many koi in your pond, that’s not always healthy. An overcrowded koi pond leads to a poor quality of life, and many of the fish may die. Feedings become more competitive, and there won’t be as much oxygen in the water if you have too many fish.

A 1,000-gallon koi pond should only have 3-4 koi fish in most cases. This gives the koi plenty of room to swim, hide, and eat. It also ensures that the oxygen level will stay healthy, especially if you put plants in the water.

The more koi there are in a pond, the higher the chances of high toxin levels. Some people put 5-10 koi in a 1,000-gallon pond, but that is somewhat dangerous. Koi fish can grow to be up to 15” long, so they will take up more room than you first expect.

5. Using The Wrong Substrate

It’s easy to pick the wrong substrate for a koi pond, and that’s not your fault. The most common substrate problem comes when koi eat the substrate. They aren’t discriminatory when it comes to food, so you must choose a substrate that they are unlikely to eat.

For example, chunky gravel is much less appetizing to koi than a smaller substrate that’s easy to eat. A nice mixture of gravel and sand can provide a great base for your koi pond. It’s also hard to agitate gravel and sand, so the water will stay clean.

That said, you must consider that heavy storms can stir up the substrate on the bottom of your koi pond. Gravel helps healthy bacteria grow, but it’s a great idea to look for gravel that consists of bigger rocks. That will reduce the choking hazard and provide plenty of surface area for good bacteria in the pond.

6. Overfeeding

Overfeeding is one of the biggest threats to any koi pond. Koi are unlikely to eat the extra food you provide, and the food will sit at the bottom of the pond. The food can eventually decompose and cause harmful bacteria to build up.

Not only does this waste food, but it can also cause algae to thrive. It’s also quite hard to remove uneaten food from the floor of your koi pond unless you get in the water. You only need to feed koi once per day in cold climates, and 2-4 times per day in warm climates.

The warmer it is, the more active your koi will become. Because of that, they need food more often to make up for the loss of calories.

7. Poor Filtration

Much like fish tanks, koi ponds need strong filtration systems to stay clean. Pond filters cost between $180 and $400, and they are worth every penny. They help filter fish waste and bacteria that can be harmful if they accumulate.

It’s also vital to clean your koi pond filter at least 3 times per year. Ideally, you should clean the filter in spring, fall, and winter. You can clean the filter during summer as well if you notice your koi pond is particularly dirty.

Run the filter constantly to avoid problems with algae, bacteria, and debris that can disrupt your fish. You should even clean self-cleaning pond filters, as they can become riddled with sludge.

Can You Go On Vacation If You Have A Koi Pond?

You can go on vacation if you have a koi pond, but you will need some help. The koi fish will still need food, so you’ll need to enlist the help of some friends, neighbors, or family members. Depending on how long you’re gone, your helper will likely only need to feed the fish for you.

This is a big commitment if the outdoor temperature is 70 degrees or higher, as they will need more food. Because of that, you may need to ask your helper to feed the koi up to 4 times per day. Make sure to clean the filter before you go on vacation if it’s been more than 3-4 months since the last cleaning.

Summing It Up

Overfeeding, overcrowding, and too many plants are the biggest koi pond mistakes. It’s also a mistake to use small pebbles as substrate, as it creates a choking hazard for the fish. Make sure to clean the filter in your pond 3-4 times per year, and only keep 4 full-size koi per 1,000-gallon pond.

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Nick Durante
Nick Durante

Nick Durante is a professional writer with a primary focus on home improvement. When he is not writing about home improvement or taking on projects around the house, he likes to read and create art. He is always looking towards the newest trends in home improvement.

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