A Complete Guide to Koi Fish (How To Take Care, Food, Disease, Etc.)

Actually, keeping koi fish is not a hobby or a new thing. In fact, in my opinion, the phenomenon of keeping koi fish which is very booming today has happened a long time ago.

I remember when I was in elementary school, at that time my uncle made a koi pond in the yard. Maybe it’s because he’s an architect, so at that time the pool was made of terraces and it looked quite artistic to me, who was still in elementary school at that time.

So, you could say I’ve known koi fish since elementary school. Since then I also started to like fish and started raising betta fish.

A brief history of koi fish

Koi fish is actually a derivative of the goldfish ( Eurasian carp ). Goldfish that came from China in ancient times did have a variety of colors. Then, the goldfish began to be cultivated in Japan to get various types of beautiful colors.

After that, become a koi fish that is very famous now and Japan is a country that can be said to create koi fish with various colors. So, koi fish can be said to have been ingrained in Japan.

How to keep koi fish

Koi fish are arguably one of the strongest fish to survive. If koi fish are cared for properly, koi fish can live for decades. In fact, the oldest koi fish in the world live to be 226 years old.

The koi fish named Hanako finally died in 1977, after examining its scales. It turns out that Hanako is approximately 226 years old. The owner did accept Hanako as an inheritance from her family, so it makes sense that Hanako is hundreds of years old.

Koi Fish Care

What is the right koi pond size?

Frankly I very rarely see koi fish kept in an aquarium. Most of the koi fish that I have seen are kept in ponds that are located outdoors. This is not without reason, the reason is that koi fish can grow to a large size. Of course, the size of this koi fish varies based on where you buy it.

If koi fish are kept in an aquarium, the aquarium will very quickly become too small for koi fish. Then, the koi fish will not have too much room to move later when its body is too big. I once asked my cousin who keeps koi fish about the difference between imported and local koi fish. According to him, imported koi fish from Japan tend to be larger in size than local koi fish bred in Indonesia. Of course in terms of price will also be different.

So, if you want to keep koi fish, you should prepare enough space to make an outdoor pond. Ponds for koi fish don’t have to be direct, which is good like a permanent pond, but you can start with a tarpaulin pond, for example, which is much cheaper and easier to build.

If possible, the koi fish pond should be made so that it can accommodate a minimum of 2000 liters – 3000 liters of water. This amount will vary depending on the size of the koi that you are going to keep. Of course, the more water that can be accommodated, the bigger the pond will be and will be able to accommodate koi fish with a larger number and size.

So, you need to make sure what size koi fish you will keep in order to maximize the size of the pond later. Oh yeah, a little extra information. You need to know that koi fish can jump out of the pond. This often happens to my uncle’s koi fish.

So to avoid koi fish jumping out, maybe you can put a net or other cover over your pond.

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How many koi fish are right?

So, after you decide to make a koi pond outside your house. You also have to think about how big a pool you can make. This will later become very important when you are going to raise koi fish. You should never keep too many koi fish (or any fish in fact) in a pond or aquarium.

If you keep too many koi fish, it will increase your susceptibility to disease and death. Why is that? Because the more koi fish that are kept, the more dirt will be produced. Not only dirt, but also food will be more and the possibility of any remaining will also be higher. If a large number of fish, a lot of dirt, and also a lot of food waste is not balanced with a large amount of water in the pond and an adequate filtration system, it will cause high levels of ammonia in the water.

In other words, your koi fish can be poisoned by ammonia simply because the amount is too much and not proportional to the amount of water and the pond filtration system. To avoid keeping koi fish with excessive amounts, you should use a standard amount of water. For example, you want to keep koi fish with a maximum size of 50 cm. To keep koi fish of this size, you need at least 1000 liters of water for 1/2 fish with a maximum size of 50 cm.

So, if your pond can hold 3000 liters of water, the most appropriate amount to keep koi fish with a maximum size of 50 cm is around 3-6 tails. Of course, the number of fish that can be kept will increase if the size of the koi fish is smaller than 50 cm. For example, for a koi fish of about 25 cm in size, it can maintain about 5 tails for 1000 liters of water.

How is the koi pond filtration system?

Koi Fish Food

Clean water is the most important element that must be maintained when keeping not only koi fish, but all types of fish. Although koi fish are not fussy fish, they can withstand their environment. Of course, providing the best water conditions will extend the life of your favorite koi fish.

This is where the important role of the filtration system. To keep water conditions clean and ammonia levels low, you need a good filtration system. You can divide the filtration system into several parts, for example the pre-filter, and the filter section. The pre-filter section can be filled with a filter which will filter out any deposits or fine dust that has been absorbed into the filter.

This section can also be called a mechanical filter, usually filled with a layer of sponge to separate fine dust from entering the next filtration section. The next part is the biological filter. This is where the decomposing bacteria will eat the ammonia and turn it into nitrate which is much safer for fish.

Biological filters can usually be filled with ceramic balls, plastic balls, or hollow stones. The point is to live and breed ammonia-decomposing bacteria. So, after the biological filter, then the water is ready to be returned to the pool. So that the condition and quality of water is maintained. The most important thing is to use a filtration system that suits the number of fish. This is where the importance of planning when making a koi fish pond.

You can just make an overkill filtration system just in case when the pond contains a lot of koi fish. However, it is likely that the money required will also be quite a lot. So, there needs to be a balance between the number of fish, the amount of water in the pond, and a filtration system to get a koi pond with good conditions and with a budget that fits in the pocket as well.

Do koi fish need an aerator?

Not only koi fish, but all fish need oxygen to survive in the water. Of course you can use an aerator to increase the dissolved oxygen in the water. However, using an aerator to increase dissolved oxygen levels is not the only way. Another way that can be done is to add a shower or waterfall for example.

That way, there will be movement of water so that there will be an exchange of oxygen and carbon dioxide in the water. So, using an aerator is an option, but it doesn’t have to be done when your pool has a shower or waterfall that causes water to move on the surface.

However, if the fish seem to be deprived of oxygen even though there is already a fountain or waterfall, perhaps adding an aerator is the best choice. This could be because the number of fish is too much so that the dissolved oxygen is always less.

What is the best food for koi fish?

In fact, koi fish are omnivores, aka eaters of everything. In their natural habitat, koi fish can eat insects, to plants and algae. In my opinion, the best food for koi fish is the food that is the easiest for you to find. So, if it’s easiest to find food like pellets, then it’s fine to feed your koi fish pellets.

The most important thing when feeding koi fish is not to give too much.

You can feed koi fish from 1x a day to 2x a day, this depends on the filtration system and the number of fish in the pond. Problems will arise when you have a lot of koi fish and food is often given. Of course, there will be a lot of feces produced by koi fish, and possibly a lot of food residue.

Then, when the filtration system is not strong enough to clean or reduce ammonia, the koi fish can be poisoned by ammonia.

So, koi fish should be given enough food. Koi fish are very tough and can survive without food for quite a long time. So, even if you are given food once a day, it shouldn’t be a problem. The intensity of feeding again depends on the filtration system and the number of fish in the pond. If you feel that the filtration system and the number of fish in the pond are balanced, maybe you can feed more often.

What causes koi fish to die suddenly?

Just like other types of fish, koi fish also have various types of diseases that lurk. Although koi fish are strong fish in survival, that does not mean they are immune to disease. Perhaps the most well-known disease that can infect koi fish is the koi herpes virus (KHV). Usually if there are koi fish affected by this virus, then most of the koi fish in your pond will most likely be infected and die.

Koi Fish Disease

If a fish is infected with KHV, it is likely to die within 1 to 2 days and can occur in almost any fish in the same pond. Even if some survive, it is likely that the fish still carry KHV and can infect other koi fish that have just been added to the pond. Symptoms of KHV usually include difficulty breathing, red and white injured gills, and sunken eyes.

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Besides KHV, diseases that can occur in most fish can also infect koi fish, such as dropsy and ich. How to prevent koi fish from getting sick lies in the quality of the water. Water quality must be ensured to remain good by using an adequate filtration system as well. Also, when buying or adding new fish to a pond that already has koi in it, it’s a good idea to quarantine the new fish for a few weeks.

Quarantine the fish in a separate place, this place can use an aquarium or a large bucket equipped with a filter and aerator. During this quarantine period, the condition of the new fish is checked and it is confirmed that they are not sick and carrying diseases that may be transmitted to other fish.